Elevated plasma β-hydroxybutyrate predicts adverse outcomes and disease progression in patients with arrhythmogenic cardiomyopathy

Circulating ketone bodies, genetic susceptibility, with left atrial structure, function and atrial fibrillation: A prospective study from UK Biobank

BACKGROUND

Ketone bodies (KB) are important cardiac metabolic energy source. Metabolic remodeling has been recently pointed to play an important role in the pathological process of atrial fibrillation (AF).

OBJECTIVE

To evaluate the associations between circulating KB levels with incident AF risk in the general population.

METHODS

We studied 237,163 participants (mean age, 56.5 years; 55% women) from the UK Biobank who were free of AF at baseline and had data about circulating β-hydroxybutyrate (β-OHB), acetoacetate, and acetone. The associations between KB with new-onset AF were evaluated by Cox regression in the general population and across three genetic risk groups [low, moderate, and high polygenic risk score of AF].

RESULTS

During a median follow-up of 14.8 years, 16,638 (7.0%) participants developed AF. There was a U-shaped association between total KB and β-OHB with incident AF, with nadirs at 60.6 and 40.8 μmol/L, respectively (P non-linear <0.05), whereas a positive association between acetoacetate and acetone with AF was observed (P overall <0.001, P non-linear >0.05). Consistently, a U-shaped association was observed between total KB and β-OHB with left atrial (LA) volume parameters, including LA maximum volume (LAVmax), LA minimum volume (LAVmin), and their body surface area-indexed counterparts, and an inverted U-shaped association was observed for LA ejection fraction (all P non-linear <0.05). The association between KB with AF was greater among individuals with low genetic risk (Pinteraction <0.05), while the highest AF risk was for those at high genetic risk with high KB levels. Significant mediation effects of inflammatory markers on the associations between KB and AF were identified.

CONCLUSIONS

There was a U-shaped association between circulating total KB and β-OHB with incident AF, as well as a positive association between acetoacetate and acetone level with AF risk in the general population.

Integrative proteomic and metabolomic elucidation of cardiomyopathy with in vivo and in vitro models and clinical samples

Cardiomyopathy is a prevalent cardiovascular disease that affects individuals of all ages and can lead to life-threatening heart failure. Despite its variety in types, each with distinct characteristics and causes, our understanding of cardiomyopathy at a systematic biology level remains incomplete. Mass spectrometry-based techniques have emerged as powerful tools, providing a comprehensive view of the molecular landscape and aiding in the discovery of biomarkers and elucidation of mechanisms. This review highlights the significant potential of integrating proteomic and metabolomic approaches with specialized databases to identify biomarkers and therapeutic targets across different types of cardiomyopathies. In vivo and in vitro models, such as genetically modified mice, patient-derived or induced pluripotent stem cells, and organ chips, are invaluable in exploring the pathophysiological complexities of this disease. By integrating omics approaches with these sophisticated modeling systems, our comprehension of the molecular underpinnings of cardiomyopathy can be greatly enhanced, facilitating the development of diagnostic markers and therapeutic strategies. Among the promising therapeutic targets are those involved in extracellular matrix remodeling, sarcomere damage, and metabolic remodeling. These targets hold the potential to advance precision therapy in cardiomyopathy, offering hope for more effective treatments tailored to the specific molecular profiles of patients.

Skin-interfaced microfluidic biosensors for colorimetric measurements of the concentrations of ketones in sweat

Ketones, such as beta-hydroxybutyrate (BHB), are important metabolites that can be used to monitor for conditions such as diabetic ketoacidosis (DKA) and ketosis. Compared to conventional approaches that rely on samples of urine or blood evaluated using laboratory techniques, processes for monitoring of ketones in sweat using on-body sensors offer significant advantages. Here, we report a class of soft, skin-interfaced microfluidic devices that can quantify the concentrations of BHB in sweat based on simple and low-cost colorimetric schemes. These devices combine microfluidic structures and enzymatic colorimetric BHB assays for selective and accurate analysis. Human trials demonstrate the broad applicability of this technology in practical scenarios, and they also establish quantitative correlations between the concentration of BHB in sweat and in blood. The results represent a convenient means for managing DKA and aspects of personal nutrition/wellness.

Arsenic exposure at environmentally relevant levels induced metabolic toxicity in development mice: Mechanistic insights from integrated transcriptome and metabolome

Emerging evidence has linked arsenic exposure and metabolic homeostasis, but the mechanism is incompletely understood, especially at relatively low concentrations. In this study, we used a mouse model to evaluate the health impacts and metabolic toxicity of arsenic exposure in drinking water at environmentally relevant levels (0.25 and 1.0 ppm). Our results indicated that arsenic damaged intestinal barrier and induced arsenic accumulation, oxidative stress, and pathological changes in the liver and illum. Interestingly, arsenic increased the hepatic triglyceride (TG) and total cholesterol (TC), while reduced serum TG and TC levels. The liver transcriptome found that arsenic exposure caused transcriptome perturbation and promoted hepatic lipid accumulation by regulating the exogenous fatty acids degradation and apolipoproteins related genes. The serum metabolomics identified 74 and 88 differential metabolites in 0.25 and 1.0 ppm, respectively. The KEGG disease and subcellular location analysis indicated that arsenic induced liver and intestinal diseases, and the mitochondrion might be the target organelle for arsenic-induced toxicity. Co-enrichment of transcriptome and metabolome identified 24 metabolites and 9 genes as metabolic toxicity biomarkers. Moreover, 40 male (20 nonalcoholic fatty liver disease (NAFLD) cases and 20 healthy controls) was further selected to validate our findings. Importantly, the significantly changed L-palmitoylcarnitine, 3-hydroxybutyric acid, 2-hydroxycaproic acid and 6 genes of Hadha, Acadl, Aldh3a2, Cpt1a, Cpt2, and Acox1 were found in the NAFLD cases. The results from integrated multi-omics and chemical-protein network analysis indicated that L-palmitoylcarnitine played a critical role in metabolic toxicity by regulating mitochondrial fatty acids β-oxidation genes (Cpt1a, Cpt2). In conclusion, these findings provided new clues for the metabolic toxicity of arsenic exposure at environmentally relevant levels, which involved in the late-life NAFLD development. Our results also contribute to understanding the human responses and phenotypic changes to this hazardous material exposure in the environment.

Possible role of β-hydroxybutyrate in inducing inflammation in alopecia areata

Alopecia areata (AA) is an autoimmune inflammatory disease characterized by non-scarring hair loss due to an immune response that targets hair follicles. The current treatment approach for AA involves the use of immunosuppressants and immunomodulators to reduce cytokine levels around affected hair follicles. Sodium-glucose cotransporter 2 (SGLT2) inhibitors have emerged as potential anti-inflammatory agents with diverse beneficial effects in various medical conditions. This study investigates the role of beta-hydroxybutyrate (BHB), a ketone body produced during SGLT2 inhibition, in the pathogenesis of AA. Serum BHB levels were found to be significantly elevated in patients with AA compared with healthy controls, with higher levels correlating with severity of hair loss. BHB treatment increased inflammatory cytokine production in outer root sheath (ORS) cells, mimicking the inflammatory conditions seen in AA. The results suggest that elevated BHB levels may exacerbate the inflammatory immune response in AA patients and may be associated with chronic hair loss and resistance to treatment. Serum BHB levels may serve as a potential marker of poor prognosis in patients with severe AA. Further research is needed to elucidate the precise role of BHB in the pathogenesis of AA and its implications for disease management.

Identification of Potential lncRNA-miRNA-mRNA Regulatory Network Contributing to Arrhythmogenic Right Ventricular Cardiomyopathy

Arrhythmogenic right ventricular cardiomyopathy (ARVC) can lead to sudden cardiac death and life-threatening heart failure. Due to its high fatality rate and limited therapies, the pathogenesis and diagnosis biomarker of ARVC needs to be explored urgently. This study aimed to explore the lncRNA-miRNA-mRNA competitive endogenous RNA (ceRNA) network in ARVC. The mRNA and lncRNA expression datasets obtained from the Gene Expression Omnibus (GEO) database were used to analyze differentially expressed mRNA (DEM) and lncRNA (DElnc) between ARVC and non-failing controls. Differentially expressed miRNAs (DEmiRs) were obtained from the previous profiling work. Using starBase to predict targets of DEmiRs and intersecting with DEM and DElnc, a ceRNA network of lncRNA-miRNA-mRNA was constructed. The DEM and DElnc were validated by real-time quantitative PCR in human heart tissue. Protein-protein interaction network and weighted gene co-expression network analyses were used to identify hub genes. A logistic regression model for ARVC diagnostic prediction was established with the hub genes and their ceRNA pairs in the network. A total of 448 DEMs (282 upregulated and 166 downregulated) were identified, mainly enriched in extracellular matrix and fibrosis-related GO terms and KEGG pathways, such as extracellular matrix organization and collagen fibril organization. Four mRNAs and two lncRNAs, including COL1A1, COL5A1, FBN1, BGN, XIST, and LINC00173 identified through the ceRNA network, were validated by real-time quantitative PCR in human heart tissue and used to construct a logistic regression model. Good ARVC diagnostic prediction performance for the model was shown in both the training set and the validation set. The potential lncRNA-miRNA-mRNA regulatory network and logistic regression model established in our study may provide promising diagnostic methods for ARVC.

Circulating 3-hydroxy butyrate predicts mortality in patients with chronic heart failure with reduced ejection fraction

AIMS

In patients with chronic heart failure with reduced ejection fraction (HFrEF), myocardial ketone metabolism is increased and short-term treatment with the ketone body 3-hydroxy butyrate (3-OHB) has beneficial haemodynamic effects. In patients with HFrEF, we investigated whether the level of circulating 3-OHB predicted all-cause mortality and sought to identify correlations between patient characteristics and circulating 3-OHB levels.

METHODS AND RESULTS

We conducted a cohort study in 218 patients with HFrEF. Plasma 3-OHB levels were measured using high-performance liquid chromatography tandem mass spectrometry. Data on all-cause mortality were obtained by reviewing the patients' medical records, which are linked to the national 'Central Person Registry' that registers the timing of all deaths in the country. Mean left ventricular ejection fraction was 35 ± 8.6%, mean age was 67 ± 10 years, 54% were New York Heart Association II, and 27% had type 2 diabetes mellitus. Median follow-up time was 7.3 (interquartile range 6.3-8.4) years. We observed large variations in 3-OHB levels between patients (median 59 μM, range: 14-694 μM). Patients with 3-OHB levels above the median displayed a markedly increased risk of death compared with those with low levels {hazard ratio [HR]: 2.1 [95% confidence interval (CI): 1.3-3.5], P = 0.003}. In a multivariate analysis, 3-OHB predicted mortality independently of known chronic heart failure risk factors [HR: 1.004 (95% CI: 1.001-1.007), P = 0.02] and with a similar statistical strength as N-terminal pro-brain natriuretic peptide (NT-proBNP) [HR: 1.0005 (95% CI: 1.000-1.001), P = 0.02]. For every 100 μmol increase in plasma 3-OHB, the hazard of death increased by 49%. The following factors significantly predicted 3-OHB levels in the univariate analysis: free fatty acids (FFAs) [β: 238 (95% CI: 185-292), P < 0.0001], age [β: 2.43 (95% CI: 1.14-3.72), P < 0.0001], plasma insulin {β: -0.28 [95% CI: -0.54-(-0.02)], P = 0.036}, body mass index {β: -3.15 [95% CI: -5.26-(-0.05)], P = 0.046}, diabetes [β: 44.49 (95% CI: 14.84-74.14), P = 0.003], glycosylated haemoglobin [β: 1.92 (95% CI: 0.24-3.59), P = 0.025], New York Heart Association class [β: 26.86 (95% CI: 5.99-47.72), P = 0.012], and NT-proBNP [β: 0.03 (95% CI: 0.01-0.04), P = 0.001]. In a multivariate analysis, only FFAs predicted 3-OHB levels [β: 216 (95% CI: 165-268), P > 0.001].

CONCLUSIONS

In patients with HFrEF, circulating 3-OHB was a strong predictor of all-cause mortality independently of NT-proBNP. Circulating FFAs were the best predictor of 3-OHB levels.

AAV9:PKP2 improves heart function and survival in a Pkp2-deficient mouse model of arrhythmogenic right ventricular cardiomyopathy

BACKGROUND

Arrhythmogenic right ventricular cardiomyopathy (ARVC) is a familial cardiac disease associated with ventricular arrhythmias and an increased risk of sudden cardiac death. Currently, there are no approved treatments that address the underlying genetic cause of this disease, representing a significant unmet need. Mutations in Plakophilin-2 (PKP2), encoding a desmosomal protein, account for approximately 40% of ARVC cases and result in reduced gene expression.

METHODS

Our goal is to examine the feasibility and the efficacy of adeno-associated virus 9 (AAV9)-mediated restoration of PKP2 expression in a cardiac specific knock-out mouse model of Pkp2.

RESULTS

We show that a single dose of AAV9:PKP2 gene delivery prevents disease development before the onset of cardiomyopathy and attenuates disease progression after overt cardiomyopathy. Restoration of PKP2 expression leads to a significant extension of lifespan by restoring cellular structures of desmosomes and gap junctions, preventing or halting decline in left ventricular ejection fraction, preventing or reversing dilation of the right ventricle, ameliorating ventricular arrhythmia event frequency and severity, and preventing adverse fibrotic remodeling. RNA sequencing analyses show that restoration of PKP2 expression leads to highly coordinated and durable correction of PKP2-associated transcriptional networks beyond desmosomes, revealing a broad spectrum of biological perturbances behind ARVC disease etiology.

CONCLUSIONS

We identify fundamental mechanisms of PKP2-associated ARVC beyond disruption of desmosome function. The observed PKP2 dose-function relationship indicates that cardiac-selective AAV9:PKP2 gene therapy may be a promising therapeutic approach to treat ARVC patients with PKP2 mutations.

Offspring of women with hyperemesis gravidarum are more likely to have cardiovascular abnormalities

BACKGROUND

Hyperemesis gravidarum (HG) is a severe form of pregnancy-related nausea and vomiting affecting 0.3-2.3% of pregnancies, which can lead to fluid, electrolyte, and acid-base imbalances, nutritional deficiencies, and weight loss, and is usually severe enough to require hospitalization. Abnormally elevated urinary ketones are commonly seen in patients with HG, and ketone bodies are free to pass through the placenta, and maternal hyperketonemia, with or without acidosis, is associated with an increased rate of stillbirth, an increased incidence of congenital anomalies, and impaired neurophysiologic development of the infant. This study investigates the obstetric outcomes of patients with HG and whether HG increases the incidence of cardiovascular disease in the offspring.

METHODS

This study included 1020 pregnant women who were hospitalized in our hospital for HG and ultimately delivered in our hospital as well as pregnant women without HG in early gestation and delivered in our hospital from January 2019-January 2020, and we collected and followed up the clinical information of the pregnant women and their offspring.

RESULTS

Pregnant women with HG were more likely to have severe urinary ketones, the rate of early miscarriage and mid-term miscarriage was significantly higher in women with HG compared to pregnant women without HG. Fetal and neonatal head and abdominal circumferences were smaller in HG group than in control group. Neonatal birth weight and length were also lower in the HG group and cardiovascular anomalies were more likely to occur in the offspring of women with HG when all births were followed up for 3 years.

CONCLUSIONS

HG may cause poor obstetric outcomes and was associated with the development of cardiovascular disease in the offspring of women with HG.

The therapeutic potential of ketones in cardiometabolic disease: impact on heart and skeletal muscle

β-Hydroxybutyrate (βOHB) is the major ketone in the body, and it is recognized as a metabolic energy source and an important signaling molecule. While ketone oxidation is essential in the brain during prolonged fasting/starvation, other organs such as skeletal muscle and the heart also use ketones as metabolic substrates. Additionally, βOHB-mediated molecular signaling events occur in heart and skeletal muscle cells, and via metabolism and/or signaling, ketones may contribute to optimal skeletal muscle health and cardiac function. Of importance, when the use of ketones for ATP production and/or as signaling molecules becomes disturbed in the presence of underlying obesity, type 2 diabetes, and/or cardiovascular diseases, these changes may contribute to cardiometabolic disease. As a result of these disturbances in cardiometabolic disease, multiple approaches have been used to elevate circulating ketones with the goal of optimizing either ketone metabolism or ketone-mediated signaling. These approaches have produced significant improvements in heart and skeletal muscle during cardiometabolic disease with a wide range of benefits that include improved metabolism, weight loss, better glycemic control, improved cardiac and vascular function, as well as reduced inflammation and oxidative stress. Herein, we present the evidence that indicates that ketone therapy could be used as an approach to help treat cardiometabolic diseases by targeting cardiac and skeletal muscles.

A novel endogenous retention-index for minimizing retention-time variations in metabolomic analysis with reversed-phase ultrahigh-performance liquid-chromatography and mass spectrometry

Consistent retention time (tR) of metabolites is vital for identification in metabolomic analysis with ultrahigh-performance liquid-chromatography (UPLC). To minimize inter-experimental tR variations from the reversed-phase UPLC-MS, we developed an endogenous retention-index (endoRI) using in-sample straight-chain acylcarnitines with different chain-length (LC, C0-C26) without additives. The endoRI-corrections reduced the tR variations caused by the combined changes of mobile phases, gradients, flow-rates, elution time, columns and temperature from up to 5.1 min-0.2 min for most metabolites in a model metabolome consisting of 91 metabolites and multiple biological matrices including human serum, plasma, fecal, urine, A549 cells and rabbit liver extracts. The endoRI-corrections also reduced the inter-batch and inter-platform tR variations from 1.5 min to 0.15 min for 95 % of detected features in the above biological samples. We further established a quantitative model between tR and LC for predicting tR values of acylcarnitines when absent in samples. This makes it possible to compare metabolites' tR from different tR databases and the UPLC-based metabolomic data from different batches.

A Genome-Wide Association Study of Serum Metabolite Profiles in Septic Shock Patients

OBJECTIVES

We sought to assess whether genetic associations with metabolite concentrations in septic shock patients could be used to identify pathways of potential importance for understanding sepsis pathophysiology.

DESIGN

Retrospective multicenter cohort studies of septic shock patients.

SETTING

All participants who were admitted to 27 participating hospital sites in three countries (Australia, New Zealand, and the United Kingdom) were eligible for inclusion.

PATIENTS

Adult, critically ill, mechanically ventilated patients with septic shock (n = 230) who were a subset of the Adjunctive Corticosteroid Treatment in Critically Ill Patients with Septic Shock trial (ClinicalTrials.gov number: NCT01448109).

INTERVENTIONS

None.

MEASUREMENTS AND MAIN RESULTS

A genome-wide association study was conducted for a range of serum metabolite levels for participants. Genome-wide significant associations (p ≤ 5 × 10-8) were found for the two major ketone bodies (3-hydroxybutyrate [rs2456680] and acetoacetate [rs2213037] and creatinine (rs6851961). One of these single-nucleotide polymorphisms (SNPs) (rs2213037) was located in the alcohol dehydrogenase cluster of genes, which code for enzymes related to the metabolism of acetoacetate and, therefore, presents a plausible association for this metabolite. None of the three SNPs showed strong associations with risk of sepsis, 28- or 90-day mortality, or Acute Physiology and Chronic Health Evaluation score (a measure of sepsis severity).

CONCLUSIONS

We suggest that the genetic associations with metabolites may reflect a starvation response rather than processes involved in sepsis pathophysiology. However, our results require further investigation and replication in both healthy and diseased cohorts including those of different ancestry.

Metabolic signatures in post-myocardial infarction heart failure, including insights into prediction, intervention, and prognosis

Heart failure (HF) is a prevalent long-term complication of myocardial infarction (MI). The incidence of post-MI HF is high, and patients with the condition have a poor prognosis. Accurate identification of individuals at high risk for post-MI HF is crucial for implementation of a protective and ideally personalized strategy to prevent fatal events. Post-MI HF is characterized by adverse cardiac remodeling, which results from metabolic changes in response to long-term ischemia. Moreover, various risk factors, including genetics, diet, and obesity, can influence metabolic pathways in patients. This review focuses on the metabolic signatures of post-MI HF that could serve as non-invasive biomarkers for early identification in high-risk populations. We also explore how metabolism participates in the pathophysiology of post-MI HF. Furthermore, we discuss the potential of metabolites as novel targets for treatment of post-MI HF and as biomarkers for prognostic evaluation. It is expected to provide valuable suggestions for the clinical prevention and treatment of post-MI HF from a metabolic perspective.

Molecular insight into arrhythmogenic cardiomyopathy caused by DSG2 mutations

Mutant desmoglein 2 (DSG2) is the second most common pathogenic gene in arrhythmogenic cardiomyopathy (ACM), accounting for approximately 10% of ACM cases. In addition to common clinical and pathological features, ACM caused by mutant DSG2 has specific characteristics, manifesting as left ventricle involvement and a high risk of heart failure. Pathological studies have shown extensive cardiomyocyte necrosis, infiltration of immune cells, and fibrofatty replacement in both ventricles, as well as abnormal desmosome structures in the hearts of humans and mice with mutant DSG2-related ACM. Although desmosome dysfunction is a common pathway in the pathogenesis of mutant DSG2-related ACM, the mechanisms underlying this dysfunction vary among mutations. Desmosome dysfunction induces cardiomyocyte injury, plakoglobin dislocation, and gap junction dysfunction, all of which contribute to the initiation and progression of ACM. Additionally, dysregulated inflammation, overactivation of transforming growth factor-beta-1 signaling and endoplasmic reticulum stress, and cardiac metabolic dysfunction contribute to the pathogenesis of ACM caused by mutant DSG2. These features demonstrate that patients with mutant DSG2-related ACM should be managed individually and precisely based on the genotype and phenotype. Further studies are needed to investigate the underlying mechanisms and to identify novel therapies to reverse or attenuate the progression of ACM caused by mutant DSG2.

Ketone bodies in right ventricular failure: A unique therapeutic opportunity

Background

Ketone bodies are pleotropic metabolites that play important roles in multiple biological processes ranging from bioenergetics to inflammation regulation via suppression of the NLRP3 inflammasome, and epigenetic modifications. Ketone bodies are elevated in left ventricular failure (LVF) and multiple approaches that increase ketone concentrations exert advantageous cardiac effects in rodents and humans. However, the relationships between ketone bodies and right ventricular failure (RVF) are relatively unexplored.

Methods

51 PAH patients were dichotomized into preserved or impaired RV function based on a cardiac index of 2.2 L/min/m2. Impaired RV function patients were further segmented into intermediate or severe RV dysfunction based on a right atrial pressure of 8 mm Hg. Serum ketone bodies acetoacetate (AcAc) and beta-hydroxybutyrate (βOHB) were quantified using ultra performance liquid chromatography and mass spectrometry. In rodent studies, male Sprague Dawley rats were assigned to three groups: control (saline injection), monocrotaline (MCT) standard chow diet (MCT-Standard), and MCT ketogenic diet (MCT-Keto). Immunoblots and confocal microscopy probed macrophage NLRP3 activation in RV extracts and sections. RV fibrosis was determined by Picrosirus Red. Echocardiography evaluated RV function. Pulmonary arteriole remodeling was assessed from histological specimens.

Results

Human RVF patients lacked a compensatory ketosis as serum AcAc and βOHB levels were not associated with hemodynamic, echocardiographic, or biochemical measures of RV dysfunction. In rodent studies, AcAc and βOHB levels were also not elevated in MCT-mediated RVF, but the ketogenic diet significantly increased AcAc and βOHB levels. MCT-Keto exhibited suppressed NLRP3 activation with a reduction in NLRP3, ASC (apoptosis-associated speck-like protein), pro-caspase-1, and interleukin-1 beta on immunoblots. Moreover, the number of ASC-positive macrophage in RV sections was reduced, RV fibrosis was blunted, and RV function was augmented in MCT-Keto rats.

Conclusion

The ketogenic response is blunted in pulmonary arterial hypertension (PAH) patients with RVF. In the MCT rat model of PAH-mediated RVF, a dietary-induced ketosis improves RV function, suppresses NLRP3 inflammasome activation, and combats RV fibrosis. The summation of these data suggest ketogenic therapies may be particularly efficacious in RVF, and therefore future studies evaluating ketogenic interventions in human RVF are warranted.

Metabolic Approaches for the Treatment of Dilated Cardiomyopathy

In dilated cardiomyopathy (DCM), where the heart muscle becomes stretched and thin, heart failure (HF) occurs, and the cardiomyocytes suffer from an energetic inefficiency caused by an abnormal cardiac metabolism. Although underappreciated as a potential therapeutic target, the optimal metabolic milieu of a failing heart is still largely unknown and subject to debate. Because glucose naturally has a lower P/O ratio (the ATP yield per oxygen atom), the previous studies using this strategy to increase glucose oxidation have produced some intriguing findings. In reality, the vast majority of small-scale pilot trials using trimetazidine, ranolazine, perhexiline, and etomoxir have demonstrated enhanced left ventricular (LV) function and, in some circumstances, myocardial energetics in chronic ischemic and non-ischemic HF with a reduced ejection fraction (EF). However, for unidentified reasons, none of these drugs has ever been tested in a clinical trial of sufficient size. Other pilot studies came to the conclusion that because the heart in severe dilated cardiomyopathy appears to be metabolically flexible and not limited by oxygen, the current rationale for increasing glucose oxidation as a therapeutic target is contradicted and increasing fatty acid oxidation is supported. As a result, treating metabolic dysfunction in HF may benefit from raising ketone body levels. Interestingly, treatment with sodium-glucose cotransporter-2 inhibitors (SGLT2i) improves cardiac function and outcomes in HF patients with or without type 2 diabetes mellitus (T2DM) through a variety of pleiotropic effects, such as elevated ketone body levels. The improvement in overall cardiac function seen in patients receiving SGLT2i could be explained by this increase, which appears to be a reflection of an adaptive process that optimizes cardiac energy metabolism. This review aims to identify the best metabolic therapeutic approach for DCM patients, to examine the drugs that directly affect cardiac metabolism, and to outline all the potential ancillary metabolic effects of the guideline-directed medical therapy. In addition, a special focus is placed on SGLT2i, which were first studied and prescribed to diabetic patients before being successfully incorporated into the pharmacological arsenal for HF patients.

Ketone Bodies in Right Ventricular Failure: A Unique Therapeutic Opportunity

Ketone bodies are pleotropic metabolites that play important roles in multiple biological processes ranging from bioenergetics to inflammation regulation via suppression of the NLRP3 inflammasome, and epigenetic modifications. Ketone bodies are elevated in left ventricular failure (LVF) and multiple approaches that increase ketone concentrations exert advantageous cardiac effects in rodents and humans. However, the relationships between ketone bodies and right ventricular failure (RVF) are relatively unexplored. Moreover, the cardioprotective properties of ketones in preclinical RVF are unknown. Here, we show a compensatory ketosis is absent in pulmonary arterial hypertension (PAH) patients with RVF. In the monocrotaline (MCT) rat model of PAH-mediated RVF, a dietary-induced ketosis improves RV function, suppresses NLRP3 inflammasome activation, and combats RV fibrosis. The summation of these data suggest ketogenic therapies may be particularly efficacious in RVF, and therefore future studies evaluating ketogenic interventions in human RVF are warranted.

Circulating ketone bodies and cardiovascular outcomes: the MESA study

AIMS

Ketone bodies (KB) are an important alternative metabolic fuel source for the myocardium. Experimental and human investigations suggest that KB may have protective effects in patients with heart failure. This study aimed to examine the association between KB and cardiovascular outcomes and mortality in an ethnically diverse population free from cardiovascular disease (CVD).

METHODS AND RESULTS

This analysis included 6796 participants (mean age 62 ± 10 years, 53% women) from the Multi-Ethnic Study of Atherosclerosis. Total KB was measured by nuclear magnetic resonance spectroscopy. Multivariable-adjusted Cox proportional hazard models were used to examine the association of total KB with cardiovascular outcomes. At a mean follow-up of 13.6 years, after adjusting for traditional CVD risk factors, increasing total KB was associated with a higher rate of hard CVD, defined as a composite of myocardial infarction, resuscitated cardiac arrest, stroke, and cardiovascular death, and all CVD (additionally included adjudicated angina) [hazard ratio, HR (95% confidence interval, CI): 1.54 (1.12-2.12) and 1.37 (1.04-1.80) per 10-fold increase in total KB, respectively]. Participants also experienced an 87% (95% CI: 1.17-2.97) increased rate of CVD mortality and an 81% (1.45-2.23) increased rate of all-cause mortality per 10-fold increase in total KB. Moreover, a higher rate of incident heart failure was observed with increasing total KB [1.68 (1.07-2.65), per 10-fold increase in total KB].

CONCLUSION

The study found that elevated endogenous KB in a healthy community-based population is associated with a higher rate of CVD and mortality. Ketone bodies could serve as a potential biomarker for cardiovascular risk assessment.

Ketones and the cardiovascular system

Ketone bodies, the main one being β-hydroxybutyrate, have emerged as important regulators of the cardiovascular system. In healthy individuals, as well as in individuals with heart failure or post-myocardial infarction, ketones provide a supplemental energy source for both the heart and the vasculature. In the failing heart, this additional energy may contribute to improved cardiac performance, whereas increasing ketone oxidation in vascular smooth muscle and endothelial cells enhances cell proliferation and prevents blood vessel rarefication. Ketones also have important actions in signaling pathways, posttranslational modification pathways and gene transcription; many of which modify cell proliferation, inflammation, oxidative stress, endothelial function and cardiac remodeling. Attempts to therapeutically increase ketone delivery to the cardiovascular system are numerous and have shown mixed results in terms of effectiveness. Here we review the bioenergetic and signaling effects of ketones on the cardiovascular system, and we discuss how ketones can potentially be used to treat cardiovascular diseases.

Elevated serum β-hydroxybutyrate, a circulating ketone metabolite, accelerates colorectal cancer proliferation and metastasis via ACAT1

Colorectal cancer (CRC) ranks third in incidence and second in mortality worldwide. Metabolic disorders are known to be closely associated with CRC. Functional metabolomics aims to translate metabolomics-derived biomarkers to disease mechanisms. Previous work based on untargeted liquid chromatography identified 30 differential metabolites of CRC. Among them, only β-hydroxybutyrate (BHB) was elevated in CRC. Here, we first confirm the increased level of β-hydroxybutyrate by targeted metabolomic analysis using an independent cohort of 400 serum samples by UPLC-QQQ-MS/MS analysis. Using appropriate cell and animal models, we find that treatment with pathological levels of β-hydroxybutyrate expedites CRC proliferation and metastasis. Out of four major rate-limiting enzymes of ketolysis, only acetyl-coenzyme A acetyltransferase1 (ACAT1) expression is increased in paired human CRC tissues. These findings suggest probable clinical relevance for the functional implications of β-hydroxybutyrate in CRC. We demonstrate that β-hydroxybutyrate may exert its tumorigenic effects via regulation of ACAT1, due to induction of downstream isocitrate dehydrogenase1 (IDH1) acetylation. Genetic silencing of ACAT1 significantly suppresses the progression of CRC and abrogates the effects of β-hydroxybutyrate both in vitro and in vivo. Overall, this study suggests that targeting β-hydroxybutyrate and its major rate-limiting enzyme ACAT1 may provide a new avenue for therapeutic intervention in CRC.

Ketones and the Heart: Metabolic Principles and Therapeutic Implications

The ketone bodies beta-hydroxybutyrate and acetoacetate are hepatically produced metabolites catabolized in extrahepatic organs. Ketone bodies are a critical cardiac fuel and have diverse roles in the regulation of cellular processes such as metabolism, inflammation, and cellular crosstalk in multiple organs that mediate disease. This review focuses on the role of cardiac ketone metabolism in health and disease with an emphasis on the therapeutic potential of ketosis as a treatment for heart failure (HF). Cardiac metabolic reprogramming, characterized by diminished mitochondrial oxidative metabolism, contributes to cardiac dysfunction and pathologic remodeling during the development of HF. Growing evidence supports an adaptive role for ketone metabolism in HF to promote normal cardiac function and attenuate disease progression. Enhanced cardiac ketone utilization during HF is mediated by increased availability due to systemic ketosis and a cardiac autonomous upregulation of ketolytic enzymes. Therapeutic strategies designed to restore high-capacity fuel metabolism in the heart show promise to address fuel metabolic deficits that underpin the progression of HF. However, the mechanisms involved in the beneficial effects of ketone bodies in HF have yet to be defined and represent important future lines of inquiry. In addition to use as an energy substrate for cardiac mitochondrial oxidation, ketone bodies modulate myocardial utilization of glucose and fatty acids, two vital energy substrates that regulate cardiac function and hypertrophy. The salutary effects of ketone bodies during HF may also include extra-cardiac roles in modulating immune responses, reducing fibrosis, and promoting angiogenesis and vasodilation. Additional pleotropic signaling properties of beta-hydroxybutyrate and AcAc are discussed including epigenetic regulation and protection against oxidative stress. Evidence for the benefit and feasibility of therapeutic ketosis is examined in preclinical and clinical studies. Finally, ongoing clinical trials are reviewed for perspective on translation of ketone therapeutics for the treatment of HF.

Reactivation of PPARα alleviates myocardial lipid accumulation and cardiac dysfunction by improving fatty acid β-oxidation in Dsg2-deficient arrhythmogenic cardiomyopathy

Arrhythmogenic cardiomyopathy (ACM), a fatal heart disease characterized by fibroadipocytic replacement of cardiac myocytes, accounts for 20% of sudden cardiac death and lacks effective treatment. It is often caused by mutations in desmosome proteins, with Desmoglein-2 (DSG2) mutations as a common etiology. However, the mechanism underlying the accumulation of fibrofatty in ACM remains unknown, which impedes the development of curative treatment. Here we investigated the fat accumulation and the underlying mechanism in a mouse model of ACM induced by cardiac-specific knockout of Dsg2 (CS-Dsg2 ^-/-). Heart failure and cardiac lipid accumulation were observed in CS-Dsg2 ^-/- mice. We demonstrated that these phenotypes were caused by decline of fatty acid (FA) β-oxidation resulted from impaired mammalian target of rapamycin (mTOR) signaling. Rapamycin worsened while overexpression of mTOR and 4EBP1 rescued the FA β-oxidation pathway in CS-Dsg2 ^-/- mice. Reactivation of PPARα by fenofibrate or AAV9-Pparα significantly alleviated the lipid accumulation and restored cardiac function. Our results suggest that impaired mTOR-4EBP1-PPARα-dependent FA β-oxidation contributes to myocardial lipid accumulation in ACM and PPARα may be a potential target for curative treatment of ACM.

HMGCS2 Mediation of Ketone Levels Affects Sorafenib Treatment Efficacy in Liver Cancer Cells

Primary liver cancer is the fifth leading death of cancers in men, and hepatocellular carcinoma (HCC) accounts for approximately 90% of all primary liver cancer cases. Sorafenib is a first-line drug for advanced-stage HCC patients. Sorafenib is a multi-target kinase inhibitor that blocks tumor cell proliferation and angiogenesis. Despite sorafenib treatment extending survival, some patients experience side effects, and sorafenib resistance does occur. 3-Hydroxymethyl glutaryl-CoA synthase 2 (HMGCS2) is the rate-limiting enzyme for ketogenesis, which synthesizes the ketone bodies, β-hydroxybutyrate (β-HB) and acetoacetate (AcAc). β-HB is the most abundant ketone body which is present in a 4:1 ratio compared to AcAc. Recently, ketone body treatment was found to have therapeutic effects against many cancers by causing metabolic alternations and cancer cell apoptosis. Our previous publication showed that HMGCS2 downregulation-mediated ketone body reduction promoted HCC clinicopathological progression through regulating c-Myc/cyclin D1 and caspase-dependent signaling. However, whether HMGCS2-regulated ketone body production alters the sensitivity of human HCC to sorafenib treatment remains unclear. In this study, we showed that HMGCS2 downregulation enhanced the proliferative ability and attenuated the cytotoxic effects of sorafenib by activating expressions of phosphorylated (p)-extracellular signal-regulated kinase (ERK), p-P38, and p-AKT. In contrast, HMGCS2 overexpression decreased cell proliferation and enhanced the cytotoxic effects of sorafenib in HCC cells by inhibiting ERK activation. Furthermore, we showed that knockdown HMGCS2 exhibited the potential migratory ability, as well as decreasing zonula occludens protein (ZO)-1 and increasing c-Myc expression in both sorafenib-treated Huh7 and HepG2 cells. Although HMGCS2 overexpression did not alter the migratory effect, expressions of ZO-1, c-Myc, and N-cadherin decreased in sorafenib-treated HMGCS2-overexpressing HCC cells. Finally, we investigated whether ketone treatment influences sorafenib sensitivity. We showed that β-HB pretreatment decreased cell proliferation and enhanced antiproliferative effect of sorafenib in both Huh7 and HepG2 cells. In conclusion, this study defined the impacts of HMGCS2 expression and ketone body treatment on influencing the sorafenib sensitivity of liver cancer cells.

Targeting Myocardial Substrate Metabolism in the Failing Heart: Ready for Prime Time?

PURPOSE OF REVIEW

We review the clinical benefits of altering myocardial substrate metabolism in heart failure.

RECENT FINDINGS

Modulation of cardiac substrates (fatty acid, glucose, or ketone metabolism) offers a wide range of therapeutic possibilities which may be applicable to heart failure. Augmenting ketone oxidation seems to offer great promise as a new therapeutic modality in heart failure. The heart has long been recognized as metabolic omnivore, meaning it can utilize a variety of energy substrates to maintain adequate ATP production. The adult heart uses fatty acid as a major fuel source, but it can also derive energy from other substrates including glucose and ketone, and to some extent pyruvate, lactate, and amino acids. However, cardiomyocytes of the failing heart endure remarkable metabolic remodeling including a shift in substrate utilization and reduced ATP production, which account for cardiac remodeling and dysfunction. Research to understand the implication of myocardial metabolic perturbation in heart failure has grown in recent years, and this has raised interest in targeting myocardial substrate metabolism for heart failure therapy. Due to the interdependency between different pathways, the main therapeutic metabolic approaches include inhibiting fatty acid uptake/fatty acid oxidation, reducing circulating fatty acid levels, increasing glucose oxidation, and augmenting ketone oxidation.

β-Hydroxybutyrate in Cardiovascular Diseases : A Minor Metabolite of Great Expectations

Despite recent advances in therapies, cardiovascular diseases ( CVDs ) are still the leading cause of mortality worldwide. Previous studies have shown that metabolic perturbations in cardiac energy metabolism are closely associated with the progression of CVDs. As expected, metabolic interventions can be applied to alleviate metabolic impairments and, therefore, can be used to develop therapeutic strategies for CVDs. β-hydroxybutyrate (β-HB) was once known to be a harmful and toxic metabolite leading to ketoacidosis in diabetes. However, the minor metabolite is increasingly recognized as a multifunctional molecular marker in CVDs. Although the protective role of β-HB in cardiovascular disease is controversial, increasing evidence from experimental and clinical research has shown that β-HB can be a “super fuel” and a signaling metabolite with beneficial effects on vascular and cardiac dysfunction. The tremendous potential of β-HB in the treatment of CVDs has attracted many interests of researchers. This study reviews the research progress of β-HB in CVDs and aims to provide a theoretical basis for exploiting the potential of β-HB in cardiovascular therapies.

β-Hydroxybutyrate Exacerbates Hypoxic Injury by Inhibiting HIF-1α-Dependent Glycolysis in Cardiomyocytes-Adding Fuel to the Fire?

PURPOSE

Ketone body oxidation yields more ATP per mole of consumed oxygen than glucose. However, whether an increased ketone body supply in hypoxic cardiomyocytes and ischemic hearts is protective or not remains elusive. The goal of this study is to determine the effect of β-hydroxybutyrate (β-OHB), the main constituent of ketone bodies, on cardiomyocytes under hypoxic conditions and the effects of ketogenic diet (KD) on cardiac function in a myocardial infarction (MI) mouse model.

METHODS

Human peripheral blood collected from patients with acute myocardial infarction and healthy volunteers was used to detect the level of β-OHB. N-terminal proB-type natriuretic peptide (NT-proBNP) levels and left ventricular ejection fractions (LVEFs) were measured to study the relationship between plasma β-OHB and cardiac function. Adult mouse cardiomyocytes and MI mouse models fed a KD were used to research the effect of β-OHB on cardiac damage. qPCR, western blot analysis, and immunofluorescence were used to detect the interaction between β-OHB and glycolysis. Live/dead cell staining and imaging, lactate dehydrogenase, Cell Counting Kit-8 assays, echocardiography, and 2,3,5-triphenyltetrazolium chloride staining were performed to evaluate the cardiomyocyte death, cardiac function, and infarct sizes.

RESULTS

β-OHB level was significantly higher in acute MI patients and MI mice. Treatment with β-OHB exacerbated cardiomyocyte death and decreased glucose absorption and glycolysis under hypoxic conditions. These effects were partially ameliorated by inhibiting hypoxia-inducible factor 1α (HIF-1α) degradation via roxadustat administration in hypoxia-stimulated cardiomyocytes. Furthermore, β-OHB metabolisms were obscured in cardiomyocytes under hypoxic conditions. Additionally, MI mice fed a KD exhibited exacerbated cardiac dysfunction compared with control chow diet (CD)-fed MI mice.

CONCLUSION

Elevated β-OHB levels may be maladaptive to the heart under hypoxic/ischemic conditions. Administration of roxadustat can partially reverse these harmful effects by stabilizing HIF-1α and inducing a metabolic shift toward glycolysis for energy production.

Postmortem Diagnosis of Ketoacidosis by Determining Beta-Hydroxybutyrate Levels in Three Types of Body Fluids by Two Different Methods

Background: Postmortem assessment of endogenous ketoacidosis is primarily focused on the determination of 3-beta-hydroxybutyrate (BHB). The aim of our study was to identify the most adequate body fluid and postmortem quantification method for assessing ketoacidosis status immediately prior to death. Material and method: We performed a prospective study on 53 cases of sudden death or in-hospital death that were considered forensic cases and could present a state of ketoacidosis prior to death, the autopsies being performed at a post-mortem interval of 24–72 h. BHB analysis was performed by Multi-Functional Monitoring System XPER Technology analyzer (method A—portable analyzer) for peripheral blood, and by BHB Assay MAK041 Kit (method B) for vitreous humor (VH) and cerebrospinal fluid (CSF). Results: We identified 11 ketoacidosis cases using method A and 9 ketoacidosis cases using method B. All nine cases of ketoacidosis identified using the MAK041 kit were confirmed with the portable analyzer. For the 2 cases of ketoacidosis identified only with the portable analyzer, the values obtained by method B were at the diagnostic limit. BHB concentrations determined in VH and CSF by method B were statistically significantly correlated with each other and with peripheral blood BHB concentration. Conclusion: BHB, a marker of ketoacidosis, should be determined post-mortem whenever a metabolic imbalance is suspected irrespective of known risk factors or obvious morphological substrate to help establish the thanatogenic mechanism. BHB quantification can easily be performed using a handheld automatic analyzer and a sample of peripheral blood as BHB levels in various body fluids correlate with each other.

Metabolic and metabolomics insights into dilated cardiomyopathy (DCM)

BACKGROUND

Dilated cardiomyopathy (DCM) is the most common form of heart muscle disease characterized by progressive dilatation and ventricular dysfunction. Metabolomics is an emerging and powerful discipline that provides a global information on the phenotype of mammalian systems via the study of endogenous and exogenous metabolites in cells, tissues and biofluids. These studies aid in the identification of biomarkers to prevent diseases in later life or help to early detect onset of diseases as well as aiding in the elucidation of disease mechanisms.

SUMMARY

Metabolomics provides a unique opportunity to discover biomarkers for DCM. This review demonstrates evidence of metabolite-based biomarkers useful for predicting, diagnosing and monitoring therapeutic interventions of DCM. Key metabolites identified as potential biomarkers for diagnosing DCM include acyl-carnitines, succinic acid, malate, methylhistidine, aspartate, methionine, phenylalanine. In terms of differentiating DCM from ICM, potential biomarkers including 1-pyrroline-2-carboxylate, norvaline, lysophosphatidylinositol (16:0/0:0), phosphatidylglycerol, fatty acid esters of hydroxy fatty acid, and phosphatidylcholine were identified. Acyl-carnitines, isoleucine and linoleic acid and tryptophan were the main biomarkers to monitor treatment response to DCM. Mapping metabolites to metabolic pathways revealed dysregulation of BCAA, glycolysis, tricarboxylic acid cycle and triacylglycerol and pentose phosphate metabolism which have therapeutic potential for DCM. This review shows several limitations including the use of small sample sizes, lack of interpretation of age and sex differences in most studies and the fact that studies have so far been limited to case-control study designs.

KEY MESSAGES

Metabolites have close proximity to disease phenotype. With recent advancements in metabolomics field, potential biomarkers for DCM have been identified based on studies using different biological and metabolomics technologies. However, multi-center studies with larger populations that will lead to validation of these identified biomarkers to enable their clinical translation and utilization are still needed.

Validation of an Arrhythmogenic Right Ventricular Cardiomyopathy Risk-Prediction Model in a Chinese Cohort

Background: The novel arrhythmogenic right ventricular cardiomyopathy (ARVC)-associated ventricular arrhythmias (VAs) risk-prediction model endorsed by Cadrin-Tourigny et al. was recently developed to estimate visual VA risk and was identified to be more effective for predicting ventricular events than the International Task Force Consensus (ITFC) criteria, and the Heart Rhythm Society (HRS) criteria. Data regarding its application in Asians are lacking. Objectives: We aimed to perform an external validation of this algorithm in the Chinese ARVC population. Methods: The study enrolled 88 ARVC patients who received implantable cardioverter-defibrillator (ICD) from January 2005 to January 2020. The primary endpoint was appropriate ICD therapies. The novel prediction model was used to calculate a priori predicted VA risk that was compared with the observed rates. Results: During a median follow-up of 3.9 years, 57 (64.8%) patients received the ICD therapy. Patients with implanted ICDs for primary prevention had non-significantly lower rates of ICD therapy than secondary prevention (5-year event rate: 0.46 (0.13–0.66) and 0.80 (0.64–0.89); log-rank p = 0.098). The validation study revealed the C-statistic of 0.833 (95% confidence interval (CI) 0.615–1.000), and the predicted and the observed patterns were similar in primary prevention patients (mean predicted–observed risk: −0.07 (95% CI −0.21, 0.09)). However, in secondary prevention patients, the C-statistic was 0.640 (95% CI 0.510–0.770) and the predicted risk was significantly underestimated (mean predicted–observed risk: −0.32 (95% CI −0.39, −0.24)). The recalibration analysis showed that the performance of the prediction model in secondary prevention patients was improved, with the mean predicted–observed risk of −0.04 (95% CI −0.10, 0.03). Conclusions: The novel risk-prediction model had a good fitness to predict arrhythmic risk in Asian ARVC patients for primary prevention, and for secondary prevention patients after recalibration of the baseline risk.

Association of Serum β-Hydroxybutyrate and Coronary Artery Disease in an Urban Chinese Population

Ketone bodies, including β-hydroxybutyrate (BHB), acetoacetate (AA), and acetone, can substitute and alternate with glucose under conditions of fuel/food deficiency. Ketone-body metabolism is increased in a myriad of tissue-metabolism disorders. Perturbations in metabolism are major contributors to coronary artery disease (CAD). We investigated the association of BHB with CAD. A total of 2,970 people of Chinese Han ethnicity were enrolled. The Gensini score was calculated for all patients who had positive findings. The serum level of BHB and other laboratory parameters were measured. The association of serum levels of metabolites with traditionally risk factors and CAD severity was analyzed. The BHB was found to be associated with some traditional risk factors of CAD and CAD severity, as determined by the Gensini score or the number of diseased regions. Moreover, BHB was associated with the T3/T1 tertiles of the Gensini score after the adjustment for traditional risk factors by multivariable logistic regression analysis. The association of BHB with CAD severity was more obvious in women. Taken together, these data suggest that the circulating BHB level is independently associated with CAD severity, and that this association is more pronounced in women.

Inflammation in the Pathogenesis of Arrhythmogenic Cardiomyopathy: Secondary Event or Active Driver?

Arrhythmogenic cardiomyopathy (ACM) is a rare inherited cardiac disease characterized by arrhythmia and progressive fibro-fatty replacement of the myocardium, which leads to heart failure and sudden cardiac death. Inflammation contributes to disease progression, and it is characterized by inflammatory cell infiltrates in the damaged myocardium and inflammatory mediators in the blood of ACM patients. However, the molecular basis of inflammatory process in ACM remains under investigated and it is unclear whether inflammation is a primary event leading to arrhythmia and myocardial damage or it is a secondary response triggered by cardiomyocyte death. Here, we provide an overview of the proposed players and triggers involved in inflammation in ACM, focusing on those studied using in vivo and in vitro models. Deepening current knowledge of inflammation-related mechanisms in ACM could help identifying novel therapeutic perspectives, such as anti-inflammatory therapy.

Left Ventricular Longitudinal Dyssynchrony by CMR Feature Tracking Is Related to Adverse Prognosis in Advanced Arrhythmogenic Cardiomyopathy

Objectives: Left ventricular (LV) involvement has been associated with unfavorable prognosis in arrhythmogenic cardiomyopathy (ACM). We aim to evaluate LV mechanics by cardiovascular magnetic resonance-feature tracking (CMR-FT) in ACM patients with right ventricular (RV) dysfunction. Methods: We retrospectively recruited ACM patients diagnosed according to the revised Task Force Criteria (rTFC) from January 2015 to July 2017. All patients underwent CMR examinations and collections of clinical, electrocardiographic data. The strain and dyssynchrony parameters of LV and RV were analyzed. These patients were followed, and primary study outcome was defined as a composite of cardiovascular events (arrhythmic events and heart transplantation), secondary study outcome included arrhythmic events. Results: Eighty-nine ACM patients (40.40 ± 13.98 years, 67.42% male) were included. LV and RV ejection fractions were 49.12 ± 12.02% and 22.28 ± 10.11%, respectively. During a median (IQR) follow-up for 18.20 (11.60-30.04) months, 30 patients experienced cardiovascular events which included 22 patients who experienced arrhythmic events. Patients with cardiovascular events had impaired LV global longitudinal strain (-10.82 ± 2.77 vs. -12.61 ± 3.18%, p = 0.010), impaired LV global circumferential strain (-11.81 ± 2.40 vs. -13.04 ± 2.83%, p = 0.044), and greater LV longitudinal dyssynchrony (LVLD) (80.98 ± 30.98 vs. 64.23 ± 25.51 ms, p = 0.012) than those without. After adjusting for age, sex, and other confounding factors, LVLD ≥89.15 ms was an independent risk factor for cardiovascular events (HR: 4.50, 95% CI: 1.94 to 10.42; p = 0.001) and for arrhythmic events (HR: 4.79, 95% CI: 1.74 to 13.20; p = 0.003). Conclusions: LVLD by CMR-FT was an independent risk factor for cardiovascular and arrhythmic events in ACM patients in advanced stage, which could provide prognostic value for this subtype.

Metabolic and Signaling Roles of Ketone Bodies in Health and Disease

Ketone bodies play significant roles in organismal energy homeostasis, serving as oxidative fuels, modulators of redox potential, lipogenic precursors, and signals, primarily during states of low carbohydrate availability. Efforts to enhance wellness and ameliorate disease via nutritional, chronobiological, and pharmacological interventions have markedly intensified interest in ketone body metabolism. The two ketone body redox partners, acetoacetate and D-β-hydroxybutyrate, serve distinct metabolic and signaling roles in biological systems. We discuss the pleiotropic roles played by both of these ketones in health and disease. While enthusiasm is warranted, prudent procession through therapeutic applications of ketogenic and ketone therapies is also advised, as a range of metabolic and signaling consequences continue to emerge. Organ-specific and cell-type-specific effects of ketone bodies are important to consider as prospective therapeutic and wellness applications increase.

Association of Circulating Ketone Bodies With Functional Outcomes After ST-Segment Elevation Myocardial Infarction

BACKGROUND

Circulating ketone bodies (KBs) are increased in patients with heart failure (HF), corresponding with increased cardiac KB metabolism and HF severity. However, the role of circulating KBs in ischemia/reperfusion remains unknown.

OBJECTIVES

This study sought to investigate longitudinal changes of KBs and their associations with functional outcomes in patients presenting with ST-segment elevation myocardial infarction (STEMI).

METHODS

KBs were measured in 369 participants from a randomized trial on early metformin therapy after STEMI. Nonfasting plasma concentrations of KBs (β-hydroxybutyrate, acetoacetate, and acetone) were measured by nuclear magnetic resonance spectroscopy at presentation, at 24 hours, and after 4 months. Myocardial infarct size and left ventricular ejection fraction (LVEF) were determined by cardiac magnetic resonance imaging at 4 months. Associations of circulating KBs with infarct size and LVEF were determined using multivariable linear regression analyses.

RESULTS

Circulating KBs were high at presentation with STEMI (median total KBs: 520 μmol/L; interquartile range [IQR]: 315-997 μmol/L). At 24 hours after reperfusion, KBs were still high compared with levels at 4-month follow-up (206 μmol/L [IQR: 174-246] vs 166 μmol/L [IQR: 143-201], respectively; P < 0.001). Increased KB concentrations at 24 hours were independently associated with larger myocardial infarct size (total KBs, per 100 μmol/L: β = 1.56; 95% confidence interval: 0.29-2.83; P = 0.016) and lower LVEF (β = -1.78; 95% CI: (-3.17 to -0.39; P = 0.012).

CONCLUSIONS

Circulating KBs are increased in patients presenting with STEMI. Higher KBs at 24 hours are associated with functional outcomes after STEMI, which suggests a potential role for ketone metabolism in response to myocardial ischemia. (Metabolic Modulation With Metformin to Reduce Heart Failure After Acute Myocardial Infarction: Glycometabolic Intervention as Adjunct to Primary Coronary Intervention in ST Elevation Myocardial Infarction (GIPS-III): a Randomized Controlled Trial; NCT01217307).

Why the diabetic heart is energy inefficient: a ketogenesis and ketolysis perspective

Lack of glucose uptake compromises metabolic flexibility and reduces energy efficiency in the diabetes mellitus (DM) heart. Although increased use of fatty acid to compensate glucose substrate has been studied, less is known about ketone body metabolism in the DM heart. Ketogenic diet reduces obesity, a risk factor for T2DM. How ketogenic diet affects ketone metabolism in the DM heart remains unclear. At the metabolic level, the DM heart differs from the non-DM heart because of altered metabolic substrate and the T1DM heart differs from the T2DM heart because of insulin levels. How these changes affect ketone body metabolism in the DM heart are poorly understood. Ketogenesis produces ketone bodies by using acetyl-CoA, whereas ketolysis consumes ketone bodies to produce acetyl-CoA, showing their opposite roles in the ketone body metabolism. Cardiac-specific transgenic upregulation of ketogenesis enzyme or knockout of ketolysis enzyme causes metabolic abnormalities leading to cardiac dysfunction. Empirical evidence demonstrates upregulated transcription of ketogenesis enzymes, no change in the levels of ketone body transporters, very high levels of ketone bodies, and reduced expression and activity of ketolysis enzymes in the T1DM heart. Based on these observations, I hypothesize that increased transcription and activity of cardiac ketogenesis enzyme suppresses ketolysis enzyme in the DM heart, which decreases cardiac energy efficiency. The T1DM heart exhibits highly upregulated ketogenesis compared with the T2DM heart because of the lack of insulin, which inhibits ketogenesis enzyme.

Ketone bodies for the failing heart: fuels that can fix the engine?

Accumulating evidence suggests that the failing heart reverts energy metabolism toward increased utilization of ketone bodies. Despite many discrepancies in the literature, evidence from both bench and clinical research demonstrates beneficial effects of ketone bodies in heart failure. Ketone bodies are readily oxidized by cardiomyocytes and can provide ancillary fuel for the energy-starved failing heart. In addition, ketone bodies may help to restore cardiac function by mitigating inflammation, oxidative stress, and cardiac remodeling. In this review, we hypothesize that a therapeutic approach intended to restore cardiac metabolism through ketone bodies could both refuel and 'repair' the failing heart.

Oxidized LDL-dependent pathway as new pathogenic trigger in arrhythmogenic cardiomyopathy

Arrhythmogenic cardiomyopathy (ACM) is hallmarked by ventricular fibro-adipogenic alterations, contributing to cardiac dysfunctions and arrhythmias. Although genetically determined (e.g., PKP2 mutations), ACM phenotypes are highly variable. More data on phenotype modulators, clinical prognosticators, and etiological therapies are awaited. We hypothesized that oxidized low-density lipoprotein (oxLDL)-dependent activation of PPARγ, a recognized effector of ACM adipogenesis, contributes to disease pathogenesis. ACM patients showing high plasma concentration of oxLDL display severe clinical phenotypes in terms of fat infiltration, ventricular dysfunction, and major arrhythmic event risk. In ACM patient-derived cardiac cells, we demonstrated that oxLDLs are major cofactors of adipogenesis. Mechanistically, the increased lipid accumulation is mediated by oxLDL cell internalization through CD36, ultimately resulting in PPARγ upregulation. By boosting oxLDL in a Pkp2 heterozygous knock-out mice through high-fat diet feeding, we confirmed in vivo the oxidized lipid dependency of cardiac adipogenesis and right ventricle systolic impairment, which are counteracted by atorvastatin treatment. The modulatory role of oxidized lipids on ACM adipogenesis, demonstrated at cellular, mouse, and patient levels, represents a novel risk stratification tool and a target for ACM pharmacological strategies.

Impact of Dietary Factors on Brugada Syndrome and Long QT Syndrome

A healthy regime is fundamental for the prevention of cardiovascular diseases (CVD). In inherited channelopathies, such as Brugada syndrome (BrS) and Long QT syndrome (LQTS), unfortunately, sudden cardiac death could be the first sign for patients affected by these syndromes. Several known factors are used to stratify the risk of developing cardiac arrhythmias, although none are determinative. The risk factors can be affected by adjusting lifestyle habits, such as a particular diet, impacting the risk of arrhythmogenic events and mortality. To date, the importance of understanding the relationship between diet and inherited channelopathies has been underrated. Therefore, we describe herein the effects of dietary factors on the development of arrhythmia in patients affected by BrS and LQTS. Modifying the diet might not be enough to fully prevent arrhythmias, but it can help lower the risk.

The Vital Role of Thanatochemistry in the Postmortem Diagnostic of Diabetic Ketoacidosis-Case Report

Diabetic ketoacidosis (DKA) is a lethal acute hyperglycemic complication of diabetes mellitus (DM) and it represents the initial manifestation of DM in about 15-20% of cases in adults and about 30-40% of cases in children. Postmortem diagnosis of DKA can only be made by applying thanatochemistry. Biochemistry applied postmortem is viewed with skepticism by many practitioners in the forensic field, completely lacking in many forensic services around the world, and especially in the national ones. This article aims to underline the importance of the postmortem application of biochemistry by reviewing the case of a person in the third decade of life who died suddenly at home due to diabetic ketoacidosis (DKA), whose autopsy was performed at an early PMI of approximately 24 h. Routine postmortem examinations (macroscopic, anatomopathological, and toxicological) could not establish a clear cause of death. When attention was turned to biochemical determinations (i.e., determination of glycated hemoglobin, glucose and ketone bodies (acetone, beta-hydroxybutyrate) in the blood, vitreous humor, and cerebrospinal fluid), the identified values clarified the thanatogenic mechanisms by establishing the diagnosis of DKA.

Whole-transcriptome Analysis of Fully Viable Energy Efficient Glycolytic-null Cancer Cells Established by Double Genetic Knockout of Lactate Dehydrogenase A/B or Glucose-6-Phosphate Isomerase

BACKGROUND/AIM

Nearly all mammalian tumors of diverse tissues are believed to be dependent on fermentative glycolysis, marked by elevated production of lactic acid and expression of glycolytic enzymes, most notably lactic acid dehydrogenase (LDH). Therefore, there has been significant interest in developing chemotherapy drugs that selectively target various isoforms of the LDH enzyme. However, considerable questions remain as to the consequences of biological ablation of LDH or upstream targeting of the glycolytic pathway.

MATERIALS AND METHODS

In this study, we explore the biochemical and whole transcriptomic effects of CRISPR-Cas9 gene knockout (KO) of lactate dehydrogenases A and B [LDHA/B double KO (DKO)] and glucose-6-phosphate isomerase (GPI KO) in the human colon cancer cell line LS174T, using Affymetrix 2.1 ST arrays.

RESULTS

The metabolic biochemical profiles corroborate that relative to wild type (WT), LDHA/B DKO produced no lactic acid, (GPI KO) produced minimal lactic acid and both KOs displayed higher mitochondrial respiration, and minimal use of glucose with no loss of cell viability. These findings show a high biochemical energy efficiency as measured by ATP in glycolysis-null cells. Next, transcriptomic analysis conducted on 48,226 mRNA transcripts reflect 273 differentially expressed genes (DEGS) in the GPI KO clone set, 193 DEGS in the LDHA/B DKO clone set with 47 DEGs common to both KO clones. Glycolytic-null cells reflect up-regulation in gene transcripts typically associated with nutrient deprivation / fasting and possible use of fats for energy: thioredoxin interacting protein (TXNIP), mitochondrial 3-hydroxy-3-methylglutaryl-CoA synthase 2 (HMGCS2), PPARγ coactivator 1α (PGC-1α), and acetyl-CoA acyltransferase 2 (ACAA2). Other changes in non-ergometric transcripts in both KOs show losses in "stemness", WNT signaling pathway, chemo/radiation resistance, retinoic acid synthesis, drug detoxification, androgen/estrogen activation, and extracellular matrix reprogramming genes.

CONCLUSION

These findings demonstrate that: 1) The "Warburg effect" is dispensable, 2) loss of the LDHAB gene is not only inconsequential to viability but fosters greater mitochondrial energy, and 3) drugs that target LDHA/B are likely to be ineffective without a plausible combination second drug target.

Association of beta-hydroxybutyrate with development of heart failure: Sex differences in a Dutch population cohort

BACKGROUND

In the failing heart, energy metabolism is shifted towards increased ketone body oxidation. Nevertheless, the association of beta-hydroxybutyrate (β-OHB) with development of heart failure (HF) remains unclear. We investigated the association between plasma β-OHB and the risk of HF in a prospective population-based cohort.

DESIGN

Plasma β-OHB concentrations were measured in 6134 participants of the PREVEND study. Risk of incident HF with reduced (HFrEF) or preserved (HFpEF) ejection fraction was estimated using multivariable-adjusted Cox regression models.

RESULTS

During median follow-up for 8.2 years, 227 subjects were diagnosed with HF (137 with HFrEF; 90 with HFpEF). Cox regression analyses revealed a significant association of higher β-OHB concentrations with incident HF (HR per 1 standard deviation increase, 1.40 (95% CI: 1.21-1.63; P < .001), which was largely attributable to HFrEF. In women, the hazard ratio (HR) for HFrEF per 1 standard deviation increase in β-OHB was 1.73 (95% confidence interval (CI): 1.17-2.56, P = .005) in age, BMI, type 2 diabetes, hypertension, myocardial infarction, smoking, alcohol consumption, total cholesterol, HDL-C, triglycerides, glucose, eGFR and UAE adjusted analysis. In men, in the same fully adjusted analysis, the HR was 1.14 (CI: 0.86-1.53, P = .36) (P < .01 for sex interaction). In N-terminal pro-brain natriuretic peptide (NT-proBNP)-stratified analysis, the age-adjusted association with HF was significant in women with higher NT-proBNP levels (P = .008).

CONCLUSIONS

This prospective study suggests that high plasma concentrations of β-OHB are associated with an increased risk of HFrEF, particularly in women. The mechanisms responsible for the sex differences of this association warrant further study.

Plasma Metabolites Alert Patients With Chest Pain to Occurrence of Myocardial Infarction

Myocardial infarction (MI) is one of the leading causes of death worldwide, and knowing the early warning signs of MI is lifesaving. To expand our knowledge of MI, we analyzed plasma metabolites in MI and non-MI chest pain cases to identify markers for alerting about MI occurrence based on metabolomics. A total of 230 volunteers were recruited, consisting of 146 chest pain patients admitted with suspected MI (85 MIs and 61 non-MI chest pain cases) and 84 control individuals. Non-MI cardiac chest pain cases include unstable angina (UA), myocarditis, valvular heart diseases, etc. The blood samples of all suspected MI cases were collected not longer than 6 h since the onset of chest pain. Gas chromatography-mass spectrometry and liquid chromatography-mass spectrometry were applied to identify and quantify the plasma metabolites. Multivariate statistical analysis was utilized to analyze the data, and principal component analysis showed MI could be clearly distinguished from non-MI chest pain cases (including UA and other cases) in the scores plot of metabolomic data, better than that based on the data constructed with medical history and clinical biochemical parameters. Pathway analysis highlighted an upregulated methionine metabolism and downregulated arginine biosynthesis in MI cases. Receiver operating characteristic curve (ROC) and adjusted odds ratio (OR) were calculated to evaluate potential markers for the diagnosis and prediction ability of MI (MI vs. non-MI cases). Finally, gene expression profiles from the Gene Expression Omnibus (GEO) database were briefly discussed to study differential metabolites' connection with plasma transcriptomics. Deoxyuridine (dU), homoserine, and methionine scored highly in ROC analysis (AUC > 0.91), sensitivity (>80%), and specificity (>94%), and they were correlated to LDH and AST (p < 0.05). OR values suggested, after adjusting for gender, age, lipid levels, smoking, type II diabetes, and hypertension history, that high levels of dU of positive logOR = 3.01, methionine of logOR = 3.48, and homoserine of logOR = 1.61 and low levels of isopentenyl diphosphate (IDP) of negative logOR = -5.15, uracil of logOR = -2.38, and arginine of logOR = -0.82 were independent risk factors of MI. Our study highlighted that metabolites belonging to pyrimidine, methionine, and arginine metabolism are deeply influenced in MI plasma samples. dU, homoserine, and methionine are potential markers to recognize MI cases from other cardiac chest pain cases after the onset of chest pains. Individuals with high plasma abundance of dU, homoserine, or methionine have increased risk of MI, too.

Metabolic Signature of Arrhythmogenic Cardiomyopathy

Arrhythmogenic cardiomyopathy (ACM) is a genetic-based cardiac disease accompanied by severe ventricular arrhythmias and a progressive substitution of the myocardium with fibro-fatty tissue. ACM is often associated with sudden cardiac death. Due to the reduced penetrance and variable expressivity, the presence of a genetic defect is not conclusive, thus complicating the diagnosis of ACM. Recent studies on human induced pluripotent stem cells-derived cardiomyocytes (hiPSC-CMs) obtained from ACM individuals showed a dysregulated metabolic status, leading to the hypothesis that ACM pathology is characterized by an impairment in the energy metabolism. However, despite efforts having been made for the identification of ACM specific biomarkers, there is still a substantial lack of information regarding the whole metabolomic profile of ACM patients. The aim of the present study was to investigate the metabolic profiles of ACM patients compared to healthy controls (CTRLs). The targeted Biocrates AbsoluteIDQ^® p180 assay was used on plasma samples. Our analysis showed that ACM patients have a different metabolome compared to CTRLs, and that the pathways mainly affected include tryptophan metabolism, arginine and proline metabolism and beta oxidation of fatty acids. Altogether, our data indicated that the plasma metabolomes of arrhythmogenic cardiomyopathy patients show signs of endothelium damage and impaired nitric oxide (NO), fat, and energy metabolism.

Alteration of m6A RNA Methylation in Heart Failure With Preserved Ejection Fraction

Background: Heart failure with preserved ejection fraction (HFpEF) is a heterogeneous disease, in which its pathogenesis is very complex and far from defined. Here, we explored the N⁶-methyladenosine (m6A) RNA methylation alteration in patients with HFpEF and mouse model of HFpEF.

Methods: In this case–control study, peripheral blood mononuclear cells (PBMCs) were separated from peripheral blood samples obtained from 16 HFpEF patients and 24 healthy controls. The change of m6A regulators was detected by quantitative real-time PCR (RT-PCR). A “two-hit” mouse model of HFpEF was induced by a high-fat diet and drinking water with 0.5 g/L of N^ω-nitro-l-arginine methyl ester (L-NAME). MeRIP-seq was used to map transcriptome-wide m6A in control mice and HFpEF mice, and the gene expression was high-throughput detected by RNA-seq.

Results: The expression of m6A writers METTL3, METTL4, and KIAA1429; m6A eraser FTO; and reader YTHDF2 was up-regulated in HFpEF patients, compared with health controls. Furthermore, the expression of FTO was also elevated in HFpEF mice. A total of 661 m6A peaks were significantly changed by MeRIP-seq. Gene Ontology (GO) analysis revealed that protein folding, ubiquitin-dependent ERAD pathway, and positive regulation of RNA polymerase II were the three most significantly altered biological processes in HFpEF. The pathways including proteasome, protein processing in the endoplasmic reticulum, and PI3K-Akt signaling pathway were significantly changed in HFpEF by Kyoto Encyclopedia of Genes and Genomes (KEGG) pathway analysis.

Conclusions: The expression pattern of m6A regulators and m6A landscape is changed in HFpEF. This uncovers a new transcription-independent mechanism of translation regulation. Therefore, our data suggest that the modulation of epitranscriptomic processes, such as m6A methylation, might be an interesting target for therapeutic interventions.

Therapeutic Potential of Ketone Bodies for Patients With Cardiovascular Disease: JACC State-of-the-Art Review

Metabolic perturbations underlie a variety of cardiovascular disease states; yet, metabolic interventions to prevent or treat these disorders are sparse. Ketones carry a negative clinical stigma as they are involved in diabetic ketoacidosis. However, evidence from both experimental and clinical research has uncovered a protective role for ketones in cardiovascular disease. Although ketones may provide supplemental fuel for the energy-starved heart, their cardiovascular effects appear to extend far beyond cardiac energetics. Indeed, ketone bodies have been shown to influence a variety of cellular processes including gene transcription, inflammation and oxidative stress, endothelial function, cardiac remodeling, and cardiovascular risk factors. This paper reviews the bioenergetic and pleiotropic effects of ketone bodies that could potentially contribute to its cardiovascular benefits based on evidence from animal and human studies.

Exercise Training Reverses Lipotoxicity-induced Cardiomyopathy by Inhibiting HMGCS2

PURPOSE

This study aimed to determine the effect of exercise training on preventing lipotoxic cardiomyopathy and to investigate the role of the 3-hydroxy-3-methylglutaryl-CoA synthase 2 (HMGCS2) and miR-344g-5p in cardiomyocytes.

METHODS

Male C57BL/6 mice were fed a 60% high-fat diet (HFD) for 12 wk then began swimming exercise or remained sedentary for 8 wk. Thereafter, cardiac function was assessed by echocardiography, and heart tissue and plasma were collected for further measurements. The molecular mechanism of exercise was investigated after treating Hmgcs2 siRNA in palmitate-induced neonatal mouse cardiomyocytes.

RESULTS

HFD induced myocardial hypertrophy and fibrosis and reduced coronary reserve and cardiac function. HMGCS2 levels increased, but junctophilin-2 (JPH2) levels decreased in HFD mice hearts. Such effects were attenuated by swimming exercise. Mechanistically, Hmgcs2 silencing prevented apoptosis and caspase-3 cleavage and elevated the expression of JPH2 in palmitate-stimulated cardiomyocytes. In addition, exercise promoted miR-344g-5p expression in HFD hearts. The overexpression of miR-344g-5p by chemical mimic reduced HMGCS2, apoptosis, and caspase-3 cleavage and elevated JPH2 expression in palmitate-induced cardiomyocytes.

CONCLUSION

Our results suggest that exercise limits lipid metabolic disorder, cardiac hypertrophy, and fibrosis and aids in the prevention of lipotoxic cardiomyopathy. Exercise-mediated cardioprotection by upregulating miR-344g-5p, which targets Hmgcs2 mRNA, prohibits HMGCS2 upregulation and thus lipotoxicity.

Beta-Hydroxybutyrate, Friend or Foe for Stressed Hearts

One of the characteristics of the failing human heart is a significant alteration in its energy metabolism. Recently, a ketone body, β-hydroxybutyrate (β-OHB) has been implicated in the failing heart’s energy metabolism as an alternative “fuel source.” Utilization of β-OHB in the failing heart increases, and this serves as a “fuel switch” that has been demonstrated to become an adaptive response to stress during the heart failure progression in both diabetic and non-diabetic patients. In addition to serving as an alternative “fuel,” β-OHB represents a signaling molecule that acts as an endogenous histone deacetylase (HDAC) inhibitor. It can increase histone acetylation or lysine acetylation of other signaling molecules. β-OHB has been shown to decrease the production of reactive oxygen species and activate autophagy. Moreover, β-OHB works as an NLR family pyrin domain-containing protein 3 (Nlrp3) inflammasome inhibitor and reduces Nlrp3-mediated inflammatory responses. It has also been reported that β-OHB plays a role in transcriptional or post-translational regulations of various genes’ expression. Increasing β-OHB levels prior to ischemia/reperfusion injury results in a reduced infarct size in rodents, likely due to the signaling function of β-OHB in addition to its role in providing energy. Sodium-glucose co-transporter-2 (SGLT2) inhibitors have been shown to exert strong beneficial effects on the cardiovascular system. They are also capable of increasing the production of β-OHB, which may partially explain their clinical efficacy. Despite all of the beneficial effects of β-OHB, some studies have shown detrimental effects of long-term exposure to β-OHB. Furthermore, not all means of increasing β-OHB levels in the heart are equally effective in treating heart failure. The best timing and therapeutic strategies for the delivery of β-OHB to treat heart disease are unknown and yet to be determined. In this review, we focus on the crucial role of ketone bodies, particularly β-OHB, as both an energy source and a signaling molecule in the stressed heart and the overall therapeutic potential of this compound for cardiovascular diseases.