Function and mechanism of histone β-hydroxybutyrylation in health and disease

The multifaceted roles of ketones in physiology

The production of ketones, referred to as ketogenesis, plays an essential role in maintaining energy homeostasis during prolonged fasting/starvation, which primarily stems from its ability to serve as a fuel source to support neuronal ATP production, thereby limiting muscle wasting. Over the years, the field has come to appreciate that ketones are much more than just a fuel source supporting neuronal metabolism, as many other oxidative organs, such as the heart and skeletal muscle, are capable of metabolizing ketones. Furthermore, ketones appear to be an important fuel source for exercising muscle. Beyond supporting ATP production, it is also becoming widely recognized that ketones are powerful signalling molecules, as they serve as ligands for G-protein coupled receptors and can even modify gene expression via regulating DNA post-translational modifications. As they play a key role in supporting whole-body physiology, it is not surprising that perturbations in ketone metabolism can contribute to various pathologies, particularly in relation to cardiometabolic diseases. Some of the strongest evidence supporting the aforementioned statement is seen for both heart failure and type 2 diabetes. Accordingly, we will review herein the multifaceted roles of ketones in supporting whole-body physiology, while interrogating the evidence to suggest whether modifying ketone metabolism may have a therapeutic role in the management of heart failure and type 2 diabetes.

Epigenetic regulation by ketone bodies in cardiac diseases and repair

Ketone bodies, particularly β-hydroxybutyrate (BHB), play an important role in the epigenetic regulation of gene expression in cardiac tissues, impacting both cardiac health and disease. This review explores the multifaceted influence of ketone bodies on epigenetic mechanisms, including histone acetylation, DNA methylation, ubiquitination, sirtuins activation, and RNA modulation. By acting as endogenous histone deacetylase inhibitors, ketone bodies enhance histone acetylation, thereby promoting the expression of genes involved in antioxidant defenses, anti-inflammatory responses, and metabolic regulation. Furthermore, BHB affects DNA methylation patterns by altering the availability of key metabolites such as S-adenosylmethionine. Ketogenic diet, which elevates BHB levels, has been shown to modulate gene expression, such as increasing FOXO3a and metallothionein 2, and improve cardiac function. This review highlights the therapeutic potential of ketone bodies in managing cardiac diseases through their epigenetic effects, underscoring the need for further research to elucidate the detailed molecular pathways and long-term impacts of these metabolic interventions.

Metabolic Sparks in the Liver: Metabolic and Epigenetic Reprogramming in Hepatic Stellate Cells Activation and Its Implications for Human Metabolic Diseases

The liver plays a fundamental role in metabolic homeostasis, integrating systemic fuel utilization with the progression of various metabolic diseases. Hepatic stellate cells (HSCs) are a key nonparenchymal cell type in the liver, which is essential for maintaining hepatic architecture in their quiescent state. However, upon chronic liver injury or metabolic stress, HSCs become activated, leading to excessive extracellular matrix deposition and pro-fibrotic signaling, ultimately positioning them as key players in liver pathology. Emerging evidence highlights the critical roles of metabolic reprogramming and epigenetic regulation in HSCs activation. HSCs activation is driven by both intrinsic fuel metabolism reprogramming and extrinsic metabolic cues from the microenvironment, while the metabolic intermediates actively reshape the epigenetic landscape, reinforcing fibrogenic transcriptional programs. In this review, we summarize recent advances in understanding how metabolic and epigenetic alterations drive HSCs activation, thereby shaping transcriptional programs that sustain fibrosis, and discuss potential therapeutic strategies to target these interconnected pathways in human metabolic diseases.

Not Just an Alternative Energy Source: Diverse Biological Functions of Ketone Bodies and Relevance of HMGCS2 to Health and Disease

Ketogenesis, a mitochondrial metabolic pathway, occurs primarily in liver, but kidney, colon and retina are also capable of this pathway. It is activated during fasting and exercise, by "keto" diets, and in diabetes as well as during therapy with SGLT2 inhibitors. The principal ketone body is β-hydroxybutyrate, a widely recognized alternative energy source for extrahepatic tissues (brain, heart, muscle, and kidney) when blood glucose is sparse or when glucose transport/metabolism is impaired. Recent studies have identified new functions for β-hydroxybutyrate: it serves as an agonist for the G-protein-coupled receptor GPR109A and also works as an epigenetic modifier. Ketone bodies protect against inflammation, cancer, and neurodegeneration. HMGCS2, as the rate-limiting enzyme, controls ketogenesis. Its expression and activity are regulated by transcriptional and post-translational mechanisms with glucagon, insulin, and glucocorticoids as the principal participants. Loss-of-function mutations occur in HMGCS2 in humans, resulting in a severe metabolic disease. These patients typically present within a year after birth with metabolic acidosis, hypoketotic hypoglycemia, hepatomegaly, steatotic liver damage, hyperammonemia, and neurological complications. Nothing is known about the long-term consequences of this disease. This review provides an up-to-date summary of the biological functions of ketone bodies with a special focus on HMGCS2 in health and disease.

Post-translational acylation of proteins in cardiac hypertrophy

Acylations are post-translational modifications in which functional groups are attached to amino acids on proteins. Most acylations (acetylation, butyrylation, crotonylation, lactylation, malonylation, propionylation and succinylation) involve lysine but cysteine (palmitoylation) and glycine (myristoylation) residues can also be altered. Acylations have important roles in physiological and pathophysiological processes, including cardiac hypertrophy and related cardiovascular diseases. These post-translational modifications influence chromatin architecture, transcriptional regulation and metabolic pathways, thereby affecting cardiomyocyte function and pathology. The dynamic interaction between these acylations and their regulatory enzymes, such as histone acetyltransferases, histone deacetylases and sirtuins, underscores the complexity of cellular homeostasis and pathological processes. Emerging evidence highlights the therapeutic potential of targeting acylations to modulate enzyme activity and metabolite levels, offering promising avenues for novel treatments. In this Review, we explore the diverse mechanisms through which acylations contribute to cardiac hypertrophy, highlighting the complexity and potential therapeutic targets in this regulatory network.

Targeting Lactic Acid Modification in Ischemic Heart Diseases: Novel Therapeutics and Mechanism

Ischemic heart disease (IHD), especially acute myocardial infarction (AMI), has a high mortality rate and poses a great threat to human health. When myocardial infarction occurs, the structure and function of the myocardium are significantly damaged, and its metabolisms switch from oxidative phosphorylation to glycolysis, producing lactate. Lactylation, as a newly discovered post-translational modification (PMT) in recent years, is involved in the regulation of gene expression, and cell proliferation. Emerging studies have revealed that lactate and lactylation modifications participate in inflammation and cardiac repair, and play an important role in cardiovascular diseases, such as myocardial infarction, myocardial fibrosis, and heart failure. Therefore, in this review, we discuss how glucose metabolism, glycolytic end-product lactate, and lactylation potentially interact with pathological processes, including inflammation, cardiac fibrosis, and heart failure. And targeting glycolysis and lactylation modification could provide a promising future for cardiovascular diseases.

Ketogenic diets and β-hydroxybutyrate in the prevention and treatment of diabetic kidney disease: current progress and future perspectives

Diabetic kidney disease (DKD) is the main cause of end-stage renal disease. Ketogenic diets (KD) is a high-fat, low-carbohydrate diet. KD produces ketone bodies to supplement energy in the case of insufficient glucose in the body. β-Hydroxybutyrate (BHB) is the main component of ketone bodies. BHB serves as "ancillary fuel" substituting (but also inducing) anti-oxidative, anti-inflammatory, and cardio-protective features by binding to several target proteins, including histone acylation modification, or G protein-coupled receptors (GPCRs). KD have been used to treat epilepsy, obesity, type-2 diabetes mellitus, polycystic ovary syndrome, cancers, and other diseases. According to recent research, KD and the induced BHB delay DKD progression by improving the metabolism of glucose and lipids, regulating autophagy, as well as alleviating inflammation, oxidative stress and fibrosis. However, due to some side-effects, the role and mechanism of action of KD and BHB in the prevention and treatment of DKD are controversial. This review focuses on recent progress in the research of KD and BHB in clinical and preclinical studies of DKD, and provides new perspectives for DKD treatment.

The role of myocardial energy metabolism perturbations in diabetic cardiomyopathy: from the perspective of novel protein post-translational modifications

Diabetic cardiomyopathy (DbCM), a significant chronic complication of diabetes, manifests as myocardial hypertrophy, fibrosis, and other pathological alterations that substantially impact cardiac function and elevate the risk of cardiovascular diseases and patient mortality. Myocardial energy metabolism disturbances in DbCM, encompassing glucose, fatty acid, ketone body and lactate metabolism, are crucial factors that contribute to the progression of DbCM. In recent years, novel protein post-translational modifications (PTMs) such as lactylation, β-hydroxybutyrylation, and succinylation have been demonstrated to be intimately associated with the myocardial energy metabolism process, and in conjunction with acetylation, they participate in the regulation of protein activity and gene expression activity in cardiomyocytes. This review examines the epigenetic pathogenesis of DbCM, primarily focusing on myocardial energy metabolism perturbations and novel PTMs associated with them. It provides a detailed analysis of the mechanisms of these novel PTMs in DbCM to enhance the understanding of DbCM pathophysiology and establish a theoretical foundation for the development of new treatment strategies for DbCM.

Ketogenic diet and β-hydroxybutyrate in osteoporosis: current progress and controversy

Diet has been proven to have significant impacts on the pathogenesis and treatment of osteoporosis. This review attempts to elucidate the current progress and controversy surrounding the ketogenic diet (KD) and β-hydroxybutyrate (BHB) in osteoporosis and offers a novel perspective on the prevention and treatment of osteoporosis. The ketogenic diet has been broadly used in the treatment of epilepsy, diabetes, obesity, and certain neoplasms by triggering ketone bodies, mainly BHB. However, in most osteoporosis-related clinical and preclinical studies, the ketogenic diet has demonstrated the detrimental effects of inhibiting bone accumulation and damaging bone microarchitecture. In contrast, BHB is thought to ameliorate osteoporosis by promoting osteoblastogenesis and inhibiting osteoclastogenesis. The main purpose of this review is to summarize the current research progress and hope that more basic and clinical experiments will focus on the similarities and differences between ketogenic diet (KD) and BHB in osteoporosis.

High-Fat Diet, Epigenetics, and Atherosclerosis: A Narrative Review

BACKGROUND/OBJECTIVES

Atherosclerosis is a chronic inflammatory disease developing and progressing in the presence of risk factors including hyperlipidemia, hypercholesterolemia, and chronic inflammation, among others. Atherosclerosis commonly precipitates as ischemic events, transient ischemic attacks, and myocardial infarction. Saturated fatty acids are risk factors; however, their association with epigenetics in the pathophysiology of atherosclerosis is not clearly understood. The preclinical and clinical trials associating atherosclerosis with epigenetics are scarcely documented, and most of the studies reported the use of drugs inhibiting methylation and histone modification to improve atherosclerosis. This narrative review aims to discuss various aspects and the association between a high-fat diet, epigenetic reprogramming, and atherosclerosis.

METHODS

A literature search with the keywords high-fat diet, epigenetics, and atherosclerosis, alone or in combination, was conducted to search for articles in the English language. Duplicate articles were removed, and articles related to the subject of this review article were included in this review.

RESULTS

A review of the literature suggests that a high-fat diet with saturated fatty acids is a risk factor for atherosclerosis, but this association is multifactorial, and epigenetics play a critical role. However, the connecting link and the underlying molecular and cellular mechanisms are not clearly understood yet and warrant more research.

CONCLUSIONS

A high-fat diet rich in saturated fatty acids is a risk factor for atherosclerosis involving epigenetic reprogramming and altered gene expression. The existing preclinical and clinical trials support the role of epigenetics and reversing it using drugs to attenuate atherosclerosis, but definitive evidence warrants larger clinical trials. Further, a high-fat diet in pregnant mothers can manifest as cardiovascular disease in offspring; caution must be taken in pregnant mothers for their diet and nutrients.

Irisin Predicts Poor Clinical Outcomes in Patients with Heart Failure with Preserved Ejection Fraction and Low Levels of N-Terminal Pro-B-Type Natriuretic Peptide

BACKGROUND

Despite existing evidence of the high predictive value of natriuretic peptides (NPs) in patients with heart failure (HF), patients treated with guideline-directed therapy who have low or near-normal NP levels are unlikely to be correctly stratified for risk of clinical outcomes. The aim of this study is to detect plausible predictors for poor one-year clinical outcomes in patients with HFpEF and low NT-proBNP treated with in accordance with conventional guidelines.

METHODS

A total of 337 patients with HF with preserved ejection fraction (HFpEF) who had low levels of N-terminal natriuretic pro-peptide (NT-proBNP) at discharge due to optimal guideline-based therapy were enrolled in the study. The course of the observation was 3 years. Echocardiography and the assessment of conventional hematological and biochemical parameters, including NT-proBNP, tumor necrosis factor-alpha, high-sensitivity C-reactive protein (hs-CRP), adropin, irisin, visfatin, and fetuin-A, were performed at baseline and at the end of the study.

RESULTS

Three-year cumulative clinical endpoints (cardiovascular death, myocardial infarction or unstable angina or acute coronary syndrome, worsening HF, sudden cardiac death, or cardiac-related surgery or all-cause death) were detected in 104 patients, whereas 233 did not meet the endpoint. After adjusting for an age ≥ 64 years and a presence of atrial fibrillation, diabetes mellitus, chronic kidney disease (CKD) stages 1-3 and dilated cardiomyopathy, the multivariable Cox regression analysis showed that an irisin level of ≤7.2 ng/mL was an independent predictor of cumulative clinical endpoint. Moreover, patients with levels of irisin > 7.2 ng/mL had a better Kaplan-Meier survival rate than those with a lower serum irisin level (≤7.2 ng/mL).

CONCLUSIONS

Multivariable analysis showed that an age ≥ 64 years; the presence of atrial fibrillation, diabetes mellitus, CKD stages 1-3 and dilated cardiomyopathy; an LAVI ≥ 39 mL/m2; and serum levels of hs-CRP ≥ 6.10 mg/L, irisin ≤ 7.2 ng/mL, and visfatin ≤ 1.1 ng/mL were predictors of poor clinical outcomes in HFpEF with low levels of NT-proBNP. A serum level of irisin ≤ 7.2 ng/mL could emerge as valuable biomarker for predicting long-term prognosis among HFpEF patients with low or near-normal levels of NT-proBNP.

Exogenous Ketones in Cardiovascular Disease and Diabetes: From Bench to Bedside

Ketone bodies are molecules produced from fatty acids in the liver that act as energy carriers to peripheral tissues when glucose levels are low. Carbohydrate- and calorie-restricted diets, known to increase the levels of circulating ketone bodies, have attracted significant attention in recent years due to their potential health benefits in several diseases. Specifically, increasing ketones through dietary modulation has been reported to be beneficial for cardiovascular health and to improve glucose homeostasis and insulin resistance. Interestingly, although excessive production of ketones may lead to life-threatening ketoacidosis in diabetic patients, mounting evidence suggests that modest levels of ketones play adaptive and beneficial roles in pancreatic beta cells, although the exact mechanisms are still unknown. Of note, Sodium-Glucose Transporter 2 (SGLT2) inhibitors have been shown to increase the levels of beta-hydroxybutyrate (BHB), the most abundant ketone circulating in the human body, which may play a pivotal role in mediating some of their protective effects in cardiovascular health and diabetes. This systematic review provides a comprehensive overview of the scientific literature and presents an analysis of the effects of ketone bodies on cardiovascular pathophysiology and pancreatic beta cell function. The evidence from both preclinical and clinical studies indicates that exogenous ketones may have significant beneficial effects on both cardiomyocytes and pancreatic beta cells, making them intriguing candidates for potential cardioprotective therapies and to preserve beta cell function in patients with diabetes.

A ketogenic diet alleviates the apoptosis of granulosa cells by inhibiting the activation of cGAS-STING signaling pathway in PCOS mice

BACKGROUND

Polycystic ovary syndrome (PCOS) is the most common cause of anovulatory infertility. The ketogenic diet (KD), a diet high in fat and low in carbohydrates, has been applied clinically for the treatment of obese women with PCOS. We have previously demonstrated that KD improved the reproductive phenotype in an androgen-induced PCOS mouse model, yet the underlying molecular mechanisms remain largely unclear. The aim of the present study was to investigate the effect of KD on the reproductive phenotype of a letrozole-induced PCOS mouse model.

METHODS

Female C57BL/6N mice were divided into three groups, designated control, letrozole, and letrozole + KD groups. Mice of control and letrozole groups were fed the control diet, whereas letrozole + KD mice were fed a KD with 89.9% (kcal) fat for 3 weeks after the PCOS mouse model was generated. β-hydroxybutyrate (BHB), the most abundant ketone body in the body, was used to treat KGN cells with testosterone (T) to simulate the KD effect on PCOS mouse ovaries in vitro.

RESULTS

Our data showed that KD treatment significantly increased blood ketone levels and reduced body weight. Ovarian functions were improved in some letrozole + KD mice. Results from in vitro experiments indicated mitochondrial damage owing to high T levels, which resulted in the leakage of cytochrome C and mitochondrial DNA into the cytosol and thus induced the activation of the intracellular caspase cascade and the cGAS-STING-NF-κB pathway, leading to granulosa cell inflammation and apoptosis. BHB exhibited certain protective effects on mitochondria of T-treated KGN cells via inhibiting the cGAS-STING pathway. Moreover, the cGAS-STING pathway was activated in ovaries of letrozole mice and was down-regulated in letrozole + KD mice.

CONCLUSION

These findings, for the first time, revealed that hyperandrogenism induced ovarian dysfunction possibly through activation of the cGAS-STING pathway, which could be partially inhibited by ketone bodies produced from KD administration.

Global Profiling of Protein Phosphorylation, Acetylation, and β-Hydroxybutyrylation in Nannochloropsis oceanica

Protein post-translational modifications (PTMs) regulate protein functions but remain poorly characterized in Nannochloropsis. This study examined three PTMs: lysine acetylation (Kac), lysine β-hydroxybutyrylation (Kbhb), and phosphorylation. Using LC-MS/MS, we identified 4571 Kac sites, 7812 Kbhb sites, and 6237 phosphorylation sites across 2455, 3109, and 2786 proteins, respectively. Subcellular localization analysis revealed significant overlaps between Kac and Kbhb proteins, primarily in the chloroplast, cytosol, and nucleus, while phosphorylated proteins were predominantly located in the nucleus and chloroplast. Motif analysis highlighted specific amino acid enrichments around modification sites, with several motifs conserved. Additionally, 529 proteins harbored all three PTMs, underscoring the potential regulatory interplay. Kac, Kbhb, and phosphorylated proteins were particularly abundant in glycolysis, the TCA cycle, carbon fixation, and lipid metabolism pathways, influencing energy production and lipid accumulation. Based on previous transcriptome data under nutrient-limited conditions, these frequently modified key enzymes appear to be vital components in the response to abiotic stress. The presence of histone modifications related to Kac and Kbhb might also point to the epigenetic regulation in gene expression and stress adaptation. This comprehensive PTM landscape in N. oceanica provides a foundation of valuable insights into future metabolic engineering and biotechnological applications.

Functions of Coenzyme A and Acyl-CoA in Post-Translational Modification and Human Disease

Coenzyme A (CoA) is synthesized from pantothenate, L-cysteine and adenosine triphosphate (ATP), and plays a vital role in diverse physiological processes. Protein acylation is a common post-translational modification (PTM) that modifies protein structure, function and interactions. It occurs via the transfer of acyl groups from acyl-CoAs to various amino acids by acyltransferase. The characteristics and effects of acylation vary according to the origin, structure, and location of the acyl group. Acetyl-CoA, formyl-CoA, lactoyl-CoA, and malonyl-CoA are typical acyl group donors. The major acyl donor, acyl-CoA, enables modifications that impart distinct biological functions to both histone and non-histone proteins. These modifications are crucial for regulating gene expression, organizing chromatin, managing metabolism, and modulating the immune response. Moreover, CoA and acyl-CoA play significant roles in the development and progression of neurodegenerative diseases, cancer, cardiovascular diseases, and other health conditions. The goal of this review was to systematically describe the types of commonly utilized acyl-CoAs, their functions in protein PTM, and their roles in the progression of human diseases.

ENL reads histone β-hydroxybutyrylation to modulate gene transcription

Histone modifications are typically recognized by chromatin-binding protein modules (referred to as 'readers') to mediate fundamental processes such as transcription. Lysine β-hydroxybutyrylation (Kbhb) is a new type of histone mark that couples metabolism to gene expression. However, the readers that prefer histone Kbhb remain elusive. This knowledge gap should be filled in order to reveal the molecular mechanism of this epigenetic regulation. Herein, we developed a chemical proteomic approach, relying upon multivalent photoaffinity probes to capture binders of the mark, and identified ENL as a novel target of H3K9bhb. Biochemical studies and CUT&Tag analysis further suggested that ENL favorably binds to H3K9bhb, and co-localizes with it on promoter regions to modulate gene expression. Notably, disrupting the interaction between H3K9bhb and ENL via structure-based mutation led to the suppressed expression of genes such MYC that drive cell proliferation. Together, our work offered a chemoproteomics approach and identified ENL as a novel histone β-hydroxybutyrylation effector that regulates gene transcription, providing new insight into the regulation mechanism and function of histone Kbhb.

Post-translational modifications of pyruvate dehydrogenase complex in cardiovascular disease

Pyruvate dehydrogenase complex (PDC) is a crucial enzyme that connects glycolysis and the tricarboxylic acid (TCA) cycle pathway. It plays an essential role in regulating glucose metabolism for energy production by catalyzing the oxidative decarboxylation of pyruvate to acetyl coenzyme A. Importantly, the activity of PDC is regulated through post-translational modifications (PTMs), phosphorylation, acetylation, and O-GlcNAcylation. These PTMs have significant effects on PDC activity under both physiological and pathophysiological conditions, making them potential targets for metabolism-related diseases. This review specifically focuses on the PTMs of PDC in cardiovascular diseases (CVDs) such as myocardial ischemia/reperfusion injury, diabetic cardiomyopathy, obesity-related cardiomyopathy, heart failure (HF), and vascular diseases. The findings from this review offer theoretical references for the diagnosis, treatment, and prognosis of CVD.

Role of novel protein acylation modifications in immunity and its related diseases

The cross-regulation of immunity and metabolism is currently a research hotspot in life sciences and immunology. Metabolic immunology plays an important role in cutting-edge fields such as metabolic regulatory mechanisms in immune cell development and function, and metabolic targets and immune-related disease pathways. Protein post-translational modification (PTM) is a key epigenetic mechanism that regulates various biological processes and highlights metabolite functions. Currently, more than 400 PTM types have been identified to affect the functions of several proteins. Among these, metabolic PTMs, particularly various newly identified histone or non-histone acylation modifications, can effectively regulate various functions, processes and diseases of the immune system, as well as immune-related diseases. Thus, drugs aimed at targeted acylation modification can have substantial therapeutic potential in regulating immunity, indicating a new direction for further clinical translational research. This review summarises the characteristics and functions of seven novel lysine acylation modifications, including succinylation, S-palmitoylation, lactylation, crotonylation, 2-hydroxyisobutyrylation, β-hydroxybutyrylation and malonylation, and their association with immunity, thereby providing valuable references for the diagnosis and treatment of immune disorders associated with new acylation modifications.

The ketone body β-Hydroxybutyrate as a fuel source of chondrosarcoma cells

Chondrosarcoma (CS) is a malignant bone tumor arising from cartilage-producing cells. The conventional subtype of CS typically develops within a dense cartilaginous matrix, creating an environment deficient in oxygen and nutrients, necessitating metabolic adaptation to ensure proliferation under stress conditions. Although ketone bodies (KBs) are oxidized by extrahepatic tissue cells such as the heart and brain, specific cancer cells, including CS cells, can undergo ketolysis. In this study, we found that KBs catabolism is activated in CS cells under nutrition-deprivation conditions. Interestingly, cytosolic β-hydroxybutyrate dehydrogenase 2 (BDH2), rather than mitochondrial BDH1, is expressed in these cells, indicating a specific metabolic adaptation for ketolysis in this bone tumor. The addition of the KB, β-Hydroxybutyrate (β-HB) in serum-starved CS cells re-induced the expression of BDH2, along with the key ketolytic enzyme 3-oxoacid CoA-transferase 1 (OXCT1) and monocarboxylate transporter-1 (MCT1). Additionally, internal β-HB production was quantified in supplied and starved cells, suggesting that CS cells are also capable of ketogenesis alongside ketolysis. These findings unveil a novel metabolic adaptation wherein nutrition-deprived CS cells utilize KBs for energy supply and proliferation.

Characterization of the Pristionchus pacificus "epigenetic toolkit" reveals the evolutionary loss of the histone methyltransferase complex PRC2

Comparative approaches have revealed both divergent and convergent paths to achieving shared developmental outcomes. Thus, only through assembling multiple case studies can we understand biological principles. Yet, despite appreciating the conservation-or lack thereof-of developmental networks, the conservation of epigenetic mechanisms regulating these networks is poorly understood. The nematode Pristionchus pacificus has emerged as a model system of plasticity and epigenetic regulation as it exhibits a bacterivorous or omnivorous morph depending on its environment. Here, we determined the "epigenetic toolkit" available to P. pacificus as a resource for future functional work on plasticity, and as a comparison with Caenorhabditis elegans to investigate the conservation of epigenetic mechanisms. Broadly, we observed a similar cast of genes with putative epigenetic function between C. elegans and P. pacificus. However, we also found striking differences. Most notably, the histone methyltransferase complex PRC2 appears to be missing in P. pacificus. We described the deletion/pseudogenization of the PRC2 genes mes-2 and mes-6 and concluded that both were lost in the last common ancestor of P. pacificus and a related species P. arcanus. Interestingly, we observed the enzymatic product of PRC2 (H3K27me3) by mass spectrometry and immunofluorescence, suggesting that a currently unknown methyltransferase has been co-opted for heterochromatin silencing. Altogether, we have provided an inventory of epigenetic genes in P. pacificus to compare with C. elegans. This inventory will enable reverse-genetic experiments related to plasticity and has revealed the first loss of PRC2 in a multicellular organism.

Oxidative Stress Biomarkers in Male Infertility: Established Methodologies and Future Perspectives

Male fertility can be affected by oxidative stress (OS), which occurs when an imbalance between the production of reactive oxygen species (ROS) and the body's ability to neutralize them arises. OS can damage cells and influence sperm production. High levels of lipid peroxidation have been linked to reduced sperm motility and decreased fertilization ability. This literature review discusses the most commonly used biomarkers to measure sperm damage caused by ROS, such as the high level of OS in seminal plasma as an indicator of imbalance in antioxidant activity. The investigated biomarkers include 8-hydroxy-2-deoxyguanosine acid (8-OHdG), a marker of DNA damage caused by ROS, and F2 isoprostanoids (8-isoprostanes) produced by lipid peroxidation. Furthermore, this review focuses on recent methodologies including the NGS polymorphisms and differentially expressed gene (DEG) analysis, as well as the epigenetic mechanisms linked to ROS during spermatogenesis along with new methodologies developed to evaluate OS biomarkers. Finally, this review addresses a valuable insight into the mechanisms of male infertility provided by these advances and how they have led to new treatment possibilities. Overall, the use of biomarkers to evaluate OS in male infertility has supplied innovative diagnostic and therapeutic approaches, enhancing our understanding of male infertility mechanisms.

Histone acylations as a mechanism for regulation of intestinal epithelial cells

Histone post-translational modifications are reversible epigenetic mechanisms that regulate chromatin structure and gene transcription. In recent years, in addition to the well-characterized histone acetylation, new acylations such as propionylation, crotonylation, butyrylation and beta-hydroxybutyrylation have been described and explored in different cell types at contexts of health and disease. Understanding how histone acylations contribute to gene expression regulation is especially important in intestinal epithelial cells (IECs) because they receive many different signals from other cells and the external environment and must adapt to maintain essential functions such as nutrient and water absorption, maintenance of tolerance and protection against pathogens. In this review, we describe how cells regulate these modifications, how they are recognized by other proteins and impact gene expression. We summarize recent studies that explored the role of these distinct epigenetic marks in the regulation of IECs and discuss their biological importance for the intestinal epithelium's adaptations to changes in metabolism and to respond to environmental signals provided, for example, by the diet, components of the intestinal microbiota and pathogens. Finally, we discuss how the histone acylations are affected by inflammatory signals and how this knowledge may provide new targets for treatment of pathologies such as the inflammatory bowel diseases.

Orthogonal Translation for Site-Specific Installation of Post-translational Modifications

Post-translational modifications (PTMs) endow proteins with new properties to respond to environmental changes or growth needs. With the development of advanced proteomics techniques, hundreds of distinct types of PTMs have been observed in a wide range of proteins from bacteria, archaea, and eukarya. To identify the roles of these PTMs, scientists have applied various approaches. However, high dynamics, low stoichiometry, and crosstalk between PTMs make it almost impossible to obtain homogeneously modified proteins for characterization of the site-specific effect of individual PTM on target proteins. To solve this problem, the genetic code expansion (GCE) strategy has been introduced into the field of PTM studies. Instead of modifying proteins after translation, GCE incorporates modified amino acids into proteins during translation, thus generating site-specifically modified proteins at target positions. In this review, we summarize the development of GCE systems for orthogonal translation for site-specific installation of PTMs.

Novel histone post-translational modifications in Alzheimer's disease: current advances and implications

Alzheimer's disease (AD) has a complex pathogenesis, and multiple studies have indicated that histone post-translational modifications, especially acetylation, play a significant role in it. With the development of mass spectrometry and proteomics, an increasing number of novel HPTMs, including lactoylation, crotonylation, β-hydroxybutyrylation, 2-hydroxyisobutyrylation, succinylation, and malonylation, have been identified. These novel HPTMs closely link substance metabolism to gene regulation, and an increasing number of relevant studies on the relationship between novel HPTMs and AD have become available. This review summarizes the current advances and implications of novel HPTMs in AD, providing insight into the deeper pathogenesis of AD and the development of novel drugs.

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.

Colonic ketogenesis, a microbiota-regulated process, contributes to blood ketones and protects against colitis in mice

Ketogenesis is considered to occur primarily in liver to generate ketones as an alternative energy source for non-hepatic tissues when glucose availability/utilization is impaired. 3-Hydroxy-3-methylglutaryl-CoA synthase-2 (HMGCS2) mediates the rate-limiting step in this mitochondrial pathway. Publicly available databases show marked down-regulation of HMGCS2 in colonic tissues in Crohn's disease and ulcerative colitis. This led us to investigate the expression and function of this pathway in colon and its relevance to colonic inflammation in mice. Hmgcs2 is expressed in cecum and colon. As global deletion of Hmgcs2 showed significant postnatal mortality, we used a conditional knockout mouse with enzyme deletion restricted to intestinal tract. These mice had no postnatal mortality. Fasting blood ketones were lower in these mice, indicating contribution of colonic ketogenesis to circulating ketones. There was also evidence of gut barrier breakdown and increased susceptibility to experimental colitis with associated elevated levels of IL-6, IL-1β, and TNF-α in circulation. Interestingly, many of these phenomena were mostly evident in male mice. Hmgcs2 expression in colon is controlled by colonic microbiota as evidenced from decreased expression in germ-free mice and antibiotic-treated conventional mice and from increased expression in a human colonic epithelial cell line upon treatment with aqueous extracts of cecal contents. Transcriptomic analysis of colonic epithelia from control mice and Hmgcs2-null mice indicated an essential role for colonic ketogenesis in the maintenance of optimal mitochondrial function, cholesterol homeostasis, and cell-cell tight-junction organization. These findings demonstrate a sex-dependent obligatory role for ketogenesis in protection against colonic inflammation in mice.

Impact of fasting & ketogenic interventions on the NLRP3 inflammasome: A narrative review

Overactivation of the NLRP3 inflammasome is implicated in chronic low-grade inflammation associated with various disease states, including obesity, type 2 diabetes, atherosclerosis, Alzheimer's disease, and Parkinson's disease. Emerging evidence, mostly from cell and animal models of disease, supports a role for ketosis in general, and the main circulating ketone body beta-hydroxybutyrate (BHB) in particular, in reducing NLRP3 inflammasome activation to improve chronic inflammation. As a result, interventions that can induce ketosis (e.g., fasting, intermittent fasting, time-restricted feeding/eating, very low-carbohydrate high-fat ketogenic diets) and/or increase circulating BHB (e.g., exogenous ketone supplementation) have garnered increasing interest for their therapeutic potential. The purpose of the present review is to summarize our current understanding of the literature on how ketogenic interventions impact the NLRP3 inflammasome across human, rodent and cell models. Overall, there is convincing evidence that ketogenic interventions, likely acting through multiple interacting mechanisms in a cell-, disease- and context-specific manner, can reduce NLRP3 inflammasome activation. The evidence supports a direct effect of BHB, although it is important to consider the myriad of other metabolic responses to fasting or ketogenic diet interventions (e.g., elevated lipolysis, low insulin, stable glucose, negative energy balance) that may also impact innate immune responses. Future research is needed to translate promising findings from discovery science to clinical application.

Histone Acyl Code in Precision Oncology: Mechanistic Insights from Dietary and Metabolic Factors

Cancer etiology involves complex interactions between genetic and non-genetic factors, with epigenetic mechanisms serving as key regulators at multiple stages of pathogenesis. Poor dietary habits contribute to cancer predisposition by impacting DNA methylation patterns, non-coding RNA expression, and histone epigenetic landscapes. Histone post-translational modifications (PTMs), including acyl marks, act as a molecular code and play a crucial role in translating changes in cellular metabolism into enduring patterns of gene expression. As cancer cells undergo metabolic reprogramming to support rapid growth and proliferation, nuanced roles have emerged for dietary- and metabolism-derived histone acylation changes in cancer progression. Specific types and mechanisms of histone acylation, beyond the standard acetylation marks, shed light on how dietary metabolites reshape the gut microbiome, influencing the dynamics of histone acyl repertoires. Given the reversible nature of histone PTMs, the corresponding acyl readers, writers, and erasers are discussed in this review in the context of cancer prevention and treatment. The evolving 'acyl code' provides for improved biomarker assessment and clinical validation in cancer diagnosis and prognosis.

Ketogenic metabolic therapy for chronic kidney disease - the pro part

Ketogenic metabolic therapy (KMT) is a medical nutrition therapy to address certain health and disease conditions. It is increasingly used for many non-communicable diseases that are rooted in abnormal metabolic health. Since chronic kidney disease (CKD) is commonly caused by overnutrition leading to hyperglycemia, insulin resistance and diabetes mellitus, the carbohydrate restriction inherent in KMT may offer a therapeutic option. Numerous studies have found that various forms of KMT are safe for individuals with CKD and may lead to improvement of renal function. This is in contrast to the current standard pharmacological approach to CKD that only slows the relentless progression towards renal failure. Kidney care providers, including physicians and dietitians, are usually not aware of non-standard dietary interventions, including KMT, and often criticize KMT due to common misconceptions and uncertainty about the underlying science, including the common misconception that KMT must involve high protein or meat consumption. This review article discusses the rationales for using KMT, including plant-dominant KMT, for treatment of CKD, clarifies common misconceptions, summarizes the results of clinical studies and discusses why KMT is emerging as an effective medical nutrition therapy (MNT) to consider for patients with kidney disease. KMT, including its plant-dominant versions, can expand a practitioner's kidney health toolbox and will likely become a first-line therapy for CKD in certain CKD-associated conditions such as obesity, metabolic syndrome and polycystic kidney disease.

Roles and Regulation of H3K4 Methylation During Mammalian Early Embryogenesis and Embryonic Stem Cell Differentiation

From generation of germ cells, fertilization, and throughout early mammalian embryonic development, the chromatin undergoes significant alterations to enable precise regulation of gene expression and genome use. Methylation of histone 3 lysine 4 (H3K4) correlates with active regions of the genome, and it has emerged as a dynamic mark throughout this timeline. The pattern and the level of H3K4 methylation are regulated by methyltransferases and demethylases. These enzymes, as well as their protein partners, play important roles in early embryonic development and show phenotypes in embryonic stem cell self-renewal and differentiation. The various roles of H3K4 methylation are interpreted by dedicated chromatin reader proteins, linking this modification to broader molecular and cellular phenotypes. In this review, we discuss the regulation of different levels of H3K4 methylation, their distinct accumulation pattern, and downstream molecular roles with an early embryogenesis perspective.

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.

Functioning and mechanisms of PTMs in renal diseases

Post-translational modifications (PTMs) are crucial epigenetic mechanisms that regulate various cellular biological processes. The use of mass spectrometry (MS)-proteomics has led to the discovery of numerous novel types of protein PTMs, such as acetylation, crotonylation, 2-hydroxyisobutyrylation, β-hydroxybutyrylation, protein propionylation and butyrylation, succinylation, malonylation, lactylation, and histone methylation. In this review, we specifically highlight the molecular mechanisms and roles of various histone and some non-histone PTMs in renal diseases, including diabetic kidney disease. PTMs exhibit diverse effects on renal diseases, which can be either protective or detrimental, depending on the specific type of protein PTMs and their respective targets. Different PTMs activate various signaling pathways in diverse renal pathological conditions, which could provide novel insights for studying epigenetic mechanisms and developing potential therapeutic strategies for renal diseases.

Epigenetic meets metabolism: novel vulnerabilities to fight cancer

Histones undergo a plethora of post-translational modifications (PTMs) that regulate nucleosome and chromatin dynamics and thus dictate cell fate. Several evidences suggest that the accumulation of epigenetic alterations is one of the key driving forces triggering aberrant cellular proliferation, invasion, metastasis and chemoresistance pathways. Recently a novel class of histone "non-enzymatic covalent modifications" (NECMs), correlating epigenome landscape and metabolic rewiring, have been described. These modifications are tightly related to cell metabolic fitness and are able to impair chromatin architecture. During metabolic reprogramming, the high metabolic flux induces the accumulation of metabolic intermediate and/or by-products able to react with histone tails altering epigenome homeostasis. The accumulation of histone NECMs is a damaging condition that cancer cells counteracts by overexpressing peculiar "eraser" enzymes capable of removing these modifications preserving histones architecture. In this review we explored the well-established NECMs, emphasizing the role of their corresponding eraser enzymes. Additionally, we provide a parterre of drugs aiming to target those eraser enzymes with the intent to propose novel routes of personalized medicine based on the identification of epi-biomarkers which might be selectively targeted for therapy. Video Abstract.

The crosstalking of lactate-Histone lactylation and tumor

Lactate was once considered to be a by-product of energy metabolism, but its unique biological value was only gradually explored with the advent of the Warburg effect. As an end product of glycolysis, lactate can act as a substrate for energy metabolism, a signal transduction molecule, a regulator of the tumor microenvironment and immune cells, and a regulator of the deubiquitination of specific enzymes, and is involved in various biological aspects of tumor regulation, including energy shuttling, growth and invasion, angiogenesis and immune escape. Furthermore, we describe a novel lactate-dependent epigenetic modification, namely histone lactylation modification, and review the progress of its study in tumors, mainly involving the reprogramming of tumor phenotypes, regulation of related gene expression, mediation of the glycolytic process in tumor stem cells (CSCs) and influence on the tumor immune microenvironment. The study of epigenetic regulation of tumor genes by histone modification is still in its infancy, and we expect that by summarizing the effects of lactate and histone modification on tumor and related gene regulation, we will clarify the scientific significance of future histone modification studies and the problems to be solved, and open up new fields for targeted tumor therapy.

A comparative metabolomics study between grain-sized moxibustion and suspended moxibustion on rats with gastric ulcers

Grain-sized moxibustion (GS-Moxi) and suspended moxibustion (S-Moxi) represent the two typical local heat therapies in Traditional Chinese Medicine (TCM) and have been extensively used in treating gastric ulcers (GU) in China. However, the difference in biological response between the two moxibustion therapies in treating GU remains unclear. Here we investigated the therapeutic effect and potential mechanistic difference underlying the two moxibustion methods. Ethanol-induced GU model was established and was treated with GS-Moxi or S-Moxi at ST36 and ST21 for 5 days separately. And then, gastric histopathological examination, immunohistochemical staining for repair factors (EGFR, VEGF, Ki67), and 1H NMR-based metabolomics analysis of plasma and stomach of rats were conducted. We found GS-Moxi and S-Moxi effectively alleviated gastric damage and significantly increased the expression of related repair factors. However, S-Moxi corrected aberrant energy metabolism and lipids metabolism in GU rats but had little effect on neurotransmitter-related metabolism, while GS-Moxi regulated energy metabolism and neurotransmitter-related metabolism in GU rats but had no effect on lipids metabolism. We further proposed that the main target of S-Moxi may be liver and vasculature, whereas GS-Moxi specially targeted the stomach via regulating nervous system. This study strongly verified the outstanding gastroprotective effects of moxibustion and enriched our understanding of the varied biological responses triggered by different moxibustion methods.

SGLT2 Inhibitors in the Treatment of Diabetic Kidney Disease: More than Just Glucose Regulation

Diabetic kidney disease (DKD) is a severe and common complication and affects a quarter of patients with type 2 diabetes mellitus (T2DM). Oxidative stress and inflammation related to hyperglycemia are interlinked and contribute to the occurrence of DKD. It was shown that sodium-glucose cotransporter-2 (SGLT2) inhibitors, a novel yet already widely used therapy, may prevent the development of DKD and alter its natural progression. SGLT2 inhibitors induce systemic and glomerular hemodynamic changes, provide metabolic advantages, and reduce inflammatory and oxidative stress pathways. In T2DM patients, regardless of cardiovascular diseases, SGLT2 inhibitors may reduce albuminuria, progression of DKD, and doubling of serum creatinine levels, thus lowering the need for kidney replacement therapy by over 40%. The molecular mechanisms behind these beneficial effects of SGLT2 inhibitors extend beyond their glucose-lowering effects. The emerging studies are trying to explain these mechanisms at the genetic, epigenetic, transcriptomic, and proteomic levels.

A (S)-3-Hydroxybutyrate Dehydrogenase Belonging to the 3-Hydroxyacyl-CoA Dehydrogenase Family Facilitates Hydroxyacid Degradation in Anaerobic Bacteria

Ketone bodies, including acetoacetate, 3-hydroxybutyrate, and acetone, are produced in the liver of animals during glucose starvation. Enzymes for the metabolism of (R)-3-hydroxybutyrate have been extensively studied, but little is known about the metabolism of its enantiomer (S)-3-hydroxybutyrate. Here, we report the characterization of a novel pathway for the degradation of (S)-3-hydroxybutyrate in anaerobic bacteria. We identify and characterize a stereospecific (S)-3-hydroxylbutyrate dehydrogenase (3SHBDH) from Desulfotomaculum ruminis, which catalyzes the reversible NAD(P)H-dependent reduction of acetoacetate to form (S)-3-hydroxybutyrate. 3SHBDH also catalyzes oxidation of d-threonine (2R, 3S) and l-allo-threonine (2S, 3S), consistent with its specificity for β-(3S)-hydroxy acids. Isothermal calorimetry experiments support a sequential mechanism involving binding of NADH prior to (S)-3-hydroxybutyrate. Homologs of 3SHBDH are present in anaerobic fermenting and sulfite-reducing bacteria, and experiments with Clostridium pasteurianum showed that 3SHBDH, acetate CoA-transferase (YdiF), and (S)-3-hydroxybutyryl-CoA dehydrogenase (Hbd) are involved together in the degradation of (S)-3-hydroxybutyrate as a carbon and energy source for growth. (S)-3-hydroxybutyrate is a human metabolic marker and a chiral precursor for chemical synthesis, suggesting potential applications of 3SHBDH in diagnostics or the chemicals industry. IMPORTANCE (R)-3-hydroxybutyrate is well studied as a component of ketone bodies produced by the liver and of bacterial polyesters. However, the biochemistry of its enantiomer (S)-3-hydroxybutyrate is poorly understood. This study describes the identification and characterization of a stereospecific (S)-3-hydroxylbutyrate dehydrogenase and its function in a metabolic pathway for the degradation of (S)-3-hydroxybutyrate as a carbon and energy source in anaerobic bacteria. (S)-3-hydroxybutyrate is a mammalian metabolic marker and a precursor for chemical synthesis and bioplastics, suggesting potential applications of these enzymes in diagnostics and biotechnology.

Protein posttranslational modifications in health and diseases: Functions, regulatory mechanisms, and therapeutic implications

Protein posttranslational modifications (PTMs) refer to the breaking or generation of covalent bonds on the backbones or amino acid side chains of proteins and expand the diversity of proteins, which provides the basis for the emergence of organismal complexity. To date, more than 650 types of protein modifications, such as the most well-known phosphorylation, ubiquitination, glycosylation, methylation, SUMOylation, short-chain and long-chain acylation modifications, redox modifications, and irreversible modifications, have been described, and the inventory is still increasing. By changing the protein conformation, localization, activity, stability, charges, and interactions with other biomolecules, PTMs ultimately alter the phenotypes and biological processes of cells. The homeostasis of protein modifications is important to human health. Abnormal PTMs may cause changes in protein properties and loss of protein functions, which are closely related to the occurrence and development of various diseases. In this review, we systematically introduce the characteristics, regulatory mechanisms, and functions of various PTMs in health and diseases. In addition, the therapeutic prospects in various diseases by targeting PTMs and associated regulatory enzymes are also summarized. This work will deepen the understanding of protein modifications in health and diseases and promote the discovery of diagnostic and prognostic markers and drug targets for diseases.

Epigenetic regulation in metabolic diseases: mechanisms and advances in clinical study

Epigenetics regulates gene expression and has been confirmed to play a critical role in a variety of metabolic diseases, such as diabetes, obesity, non-alcoholic fatty liver disease (NAFLD), osteoporosis, gout, hyperthyroidism, hypothyroidism and others. The term 'epigenetics' was firstly proposed in 1942 and with the development of technologies, the exploration of epigenetics has made great progresses. There are four main epigenetic mechanisms, including DNA methylation, histone modification, chromatin remodelling, and noncoding RNA (ncRNA), which exert different effects on metabolic diseases. Genetic and non-genetic factors, including ageing, diet, and exercise, interact with epigenetics and jointly affect the formation of a phenotype. Understanding epigenetics could be applied to diagnosing and treating metabolic diseases in the clinic, including epigenetic biomarkers, epigenetic drugs, and epigenetic editing. In this review, we introduce the brief history of epigenetics as well as the milestone events since the proposal of the term 'epigenetics'. Moreover, we summarise the research methods of epigenetics and introduce four main general mechanisms of epigenetic modulation. Furthermore, we summarise epigenetic mechanisms in metabolic diseases and introduce the interaction between epigenetics and genetic or non-genetic factors. Finally, we introduce the clinical trials and applications of epigenetics in metabolic diseases.

Ketogenic Diet Increases Serum and White Adipose Tissue SIRT1 Expression in Mice

Overnutrition and its sequelae have become a global concern due to the increasing incidence of obesity and insulin resistance. A ketogenic diet (KD) is widely used as a dietary treatment for metabolic disorders. Sirtuin1 (SIRT1), a metabolic sensor which regulates fat homeostasis, is modulated by dietary interventions. However, the influence of nutritional ketosis on SIRT1 is still debated. We examined the effect of KD on adipose tissue, liver, and serum levels of SIRT1 in mice. Adult C57BL/6J male mice were randomly assigned to two isocaloric dietary groups and fed with either high-fat KD or normal chow (NC) for 4 weeks. Serum SIRT1, beta-hydroxybutyrate (βHB), glucose, and triglyceride levels, as well as SIRT1 expression in visceral (VAT), subcutaneous (SAT), and brown (BAT) adipose tissues, and in the liver, were measured. KD-fed mice showed an increase in serum βHB in parallel with serum SIRT1 (r = 0.732, p = 0.0156), and increased SIRT1 protein expression in SAT and VAT. SIRT1 levels remained unchanged in BAT and in the liver, which developed steatosis. Normal glycemia and triglycerides were observed. Under a KD, serum and white fat phenotypes show higher SIRT1, suggesting that one of the molecular mechanisms underlying a KD's potential benefits on metabolic health involves a synergistic interaction with SIRT1.

Ketone Bodies as Metabolites and Signalling Molecules at the Crossroad between Inflammation and Epigenetic Control of Cardiometabolic Disorders

For many years, it has been clear that a Western diet rich in saturated fats and sugars promotes an inflammatory environment predisposing a person to chronic cardiometabolic diseases. In parallel, the emergence of ketogenic diets, deprived of carbohydrates and promoting the synthesis of ketone bodies imitating the metabolic effects of fasting, has been shown to provide a possible nutritional solution to alleviating diseases triggered by an inflammatory environment. The main ketone body, β-hydroxybutyrate (BHB), acts as an alternative fuel, and also as a substrate for a novel histone post-translational modification, β-hydroxybutyrylation. β-hydroxybutyrylation influences the state of chromatin architecture and promotes the transcription of multiple genes. BHB has also been shown to modulate inflammation in chronic diseases. In this review, we discuss, in the pathological context of cardiovascular risks, the current understanding of how ketone bodies, or a ketogenic diet, are able to modulate, trigger, or inhibit inflammation and how the epigenome and chromatin remodeling may be a key contributor.