Beneficial Effects of Ketone Ester in Patients With Cardiogenic Shock: A Randomized, Controlled, Double-Blind Trial

Lactate orchestrates metabolic hemodynamic adaptations through a unique combination of venocontraction, artery relaxation, and positive inotropy

AIM

H+ facilitates metabolic blood flow regulation while negatively impacting cardiac contractility. Cardiovascular consequences of conjugate bases accumulating alongside H+ remain unclear. Here, we evaluate the cardiovascular effects of nine prominent carboxylates-particularly lactate, 3-hydroxybutyrate, and butyrate-linked to metabolic and microbial activity.

METHODS

Comparing the actions of pH-adjusted Na-carboxylates to equiosmolar NaCl, we study arteries and veins isolated from healthy rats and humans with ischaemic heart disease, isolated perfused rat hearts, and rat cardiovascular function in vivo.

RESULTS

The tested carboxylates generally relax arteries and veins. L-lactate relaxes human and rat arteries up to 70% (EC50 = 10.1 mM) and rat brachial and mesenteric veins up to 30% of pre-contractions, yet stands out by augmenting contractions of rat femoral, saphenous, and lateral marginal veins and human internal thoracic and great saphenous veins up to 50%. D-lactate shows only minor actions. In isolated perfused hearts, 10 mM L-lactate increases coronary flow (17.1 ± 7.7%) and left ventricular developed pressure (10.1 ± 3.0%) without affecting heart rate. L-lactate infusion in rats-reaching 3.7 ± 0.3 mM in the circulation-increases left ventricular end-diastolic volume (11.3 ± 2.8%), stroke volume (22.6 ± 3.0%), cardiac output (23.4 ± 3.5%), and ejection fraction (10.6 ± 2.0%), and lowers systemic vascular resistance (34.1 ± 3.7%) without influencing blood pressure or heart rate. The ketone body 3-hydroxybutyrate causes lactate accumulation and elevates left ventricular end-diastolic volume in vivo.

CONCLUSION

Carboxylate metabolites generally relax arteries and veins. L-lactate relaxes arteries, lowering systemic vascular resistance, causes preferential venocontraction with increased ventricular diastolic filling, and elevates cardiac contractility and cardiac output. We propose that L-lactate optimizes cardiovascular function during metabolic disturbances.

The denitrosylase SCoR2 controls cardioprotective metabolic reprogramming

Acute myocardial infarction (MI) is a leading cause of morbidity and mortality, and therapeutic options remain limited. Endogenously generated nitric oxide (NO) is highly cardioprotective, but protection is not replicated by nitroso-vasodilators (e.g., nitrates, nitroprusside) used in clinical practice, highlighting specificity in NO-based signaling and untapped therapeutic potential. Signaling by NO is mediated largely by S-nitrosylation, entailing specific enzymes that form and degrade S-nitrosothiols in proteins (SNO-proteins), termed nitrosylases and denitrosylases, respectively. SNO-CoA Reductase 2 (SCoR2; product of the Akr1a1 gene) is a recently discovered protein denitrosylase. Genetic variants in SCoR2 have been associated with cardiovascular disease, but its function is unknown. Here we show that mice lacking SCoR2 exhibit robust protection in an animal model of MI. SCoR2 regulates ketolytic energy availability, antioxidant levels and polyol homeostasis via S-nitrosylation of key metabolic effectors. Human cardiomyopathy shows reduced SCoR2 expression and an S-nitrosylation signature of metabolic reprogramming, mirroring SCoR2-/- mice. Deletion of SCoR2 thus coordinately reprograms multiple metabolic pathways-ketone body utilization, glycolysis, pentose phosphate shunt and polyol metabolism-to limit infarct size, establishing SCoR2 as a novel regulator in the injured myocardium and a potential drug target.

Impact statement

Mice lacking the denitrosylase enzyme SCoR2/AKR1A1 demonstrate robust cardioprotection resulting from reprogramming of multiple metabolic pathways, revealing widespread, coordinated metabolic regulation by SCoR2.

Metabolic profiles associate with mortality and neurological outcomes in out-of-hospital cardiac arrest patients

BACKGROUND

Out-of-hospital cardiac arrest (OHCA) is associated with high mortality and poor neurological outcome, with significant metabolic changes upon return of spontaneous circulation (ROSC). This study aimed to investigate the association of metabolic derangements with outcomes in patients resuscitated from OHCA.

METHODS

Blood samples from 156 consecutive unconscious OHCA patients in the Targeted Temperature Management trial were analyzed at hospital admission. Metabolic parameters including free fatty acids (FFAs), glucose, lactate, 3-hydroxybutyrate (3-OHB), and insulin were measured. Hierarchical clustering categorized patients based on metabolic response patterns. Thirty-day mortality and neurological outcomes were compared across these clusters.

RESULTS

The median age was 62 years (IQR 54-68) and 87% were male. Hierarchical clustering identified three distinct metabolic profiles. Cluster A showed severe metabolic distress with elevated lactate, high insulin resistance, and modest FFA/3-OHB levels. Cluster B had low FFA/3-OHB levels while Cluster C showed high FFA/3-OHB levels; both were associated with lower lactate and insulin resistance compared with Cluster A. Cluster A was linked to greater cardiac arrest severity, including longer time to ROSC, increased defibrillations, and higher adrenaline use. Thirty-day mortality rates were: Cluster A, 68%; B, 33%; C, 21% (log-rank P < 0.001). Neurological deaths were lowest in Clusters C. Baseline FFA levels were independently associated with neurological death.

CONCLUSION

This study identifies distinct metabolic profiles associated with neurological recovery after cardiac arrest, suggesting a potential link between metabolic states and outcomes that may reflect adaptive brain resilience. These findings highlight the need for further research to explore whether metabolic-targeted interventions could enhance recovery.

On how to feed critically ill children in intensive care: A slowly shifting paradigm

Critically ill children requiring treatment in a pediatric intensive care unit (PICU) suffer from anorexia and/or feeding intolerance. The resulting macronutrient deficit associates with poor outcome. Until recently, this association formed the basis for initiating enteral or parenteral feeding early to improve outcome. The multicenter "Early-versus-Late-Parenteral-Nutrition-in-the-Pediatric-Intensive-Care-Unit" randomized controlled trial (PEPaNIC-RCT) addressed whether this association is causal. It showed that early supplementation of insufficient/contraindicated enteral nutrition with parenteral nutrition, as compared with accepting a macronutrient deficit throughout the first week in the PICU, did not improve outcome. On the contrary, it caused more infections and prolonged organ support and PICU stay, and adversely affected neurodevelopmental outcomes 2 and 4 years later. Harm was present in all subgroups and appeared explained by the macronutrient dose, more specifically the amino-acid dose, not lipid or glucose doses. These findings corroborated results from large-scale adult RCTs. Mechanisms of harm from early enhanced nutrition comprised suppressed cellular repair pathways like autophagy and ketogenesis, suppressed illness-induced alterations in thyroid hormone metabolism, more iatrogenic hyperglycemia, increased urea cycle activity through anabolic resistance, and induction of epigenetic modifications that mediate longer-term developmental impairments. These results came unexpected to many pediatric intensivists. Hence, the paradigm has only slowly begun to shift toward more restrictive macronutrient administration in the acute phase of critical illness. Benefits of early fasting responses have become clear, provided micronutrients are given to prevent deficiencies and refeeding syndrome. These insights open perspectives for studies investigating novel nutritional strategies to activate fasting-induced cellular repair while avoiding prolonged starvation.

Metabolic and Pharmacokinetic Profiling of a Ketone Ester by Background SGLT2 Inhibitor Therapy in HFrEF

Growing evidence supports therapeutic ketosis in heart failure with reduced ejection fraction, though uncertainty exists regarding use with SGLT2i and dose-dependent effects. In a phase I trial of 2 ketone ester (KE) doses in 20 heart failure with reduced ejection fraction participants, stratified by background SGLT2i, the authors detailed pharmacokinetic parameters, noting rapid ketosis and short half-life. KE was associated with lower non-esterified fatty acid, branched-chain amino acids, and most acylcarnitines (except C2 and C4-OH, which increased); differences were observed by SGLT2i and KE dose. Increases in heart rate and decreases in systolic blood pressure, pH, and bicarbonate were generally transient. KE ingestion induces rapid changes in key metabolic pathways, differentially affected by SGLT2i (fatty acid metabolism) and KE dose (ketone metabolism). Hemodynamic effects were transient and irrespective of dose or SGLT2i. (Ketone Pharmacokinetic Study in HFrEF; NCT05757193).

Myocardial metabolic flexibility following ketone infusion demonstrated by hyperpolarized [2-13C]pyruvate MRS in pigs

This study aims to investigate the effects of β-3-hydroxybutyrate (β-3-OHB) infusion on myocardial metabolic flexibility using hyperpolarized [2-13C]pyruvate magnetic resonance spectroscopy (MRS) in the pig heart. We hypothesized that β-3-OHB infusion will cause rapid, quantifiable alterations in tricarboxylic acid (TCA) cycle flux as measured non-invasively by 13C MRS and reflect myocardial work. Five female Danish landrace pigs underwent β-3-OHB infusion during a hyperinsulinemic euglycemic clamp (HEC). Cardiac metabolism and hemodynamics were monitored using hyperpolarized [2-13C]pyruvate MRS and cardiac MRI. β-3-OHB infusion during HEC resulted in significant increases in cardiac output over baseline (from 1.9 to 3.8 L/min, p = 0.0011) and heart rate (from 51 to 85 bpm, p = 0.0004). Metabolic analysis showed a shift towards increased lactate production and decreased levels of acetyl-carnitine and glutamate during β-3-OHB infusion. Following the termination of the infusion, a normalization of these metabolic markers was observed. These results demonstrate the profound metabolic adaptability of the myocardium to ketone body utilization. The infusion of Na-β-3-OHB significantly alters both the hemodynamics and metabolism of the porcine heart. The observed increase in cardiac output and metabolic shifts towards lactate production suggest that ketone bodies could potentially enhance cardiac function by providing an efficient-energy substrate that, if provided, is preferentially used. This study provides new insights into the metabolic flexibility of the heart and hints at the potential therapeutic benefits of ketone interventions in heart failure treatment.

Ketone monoester ingestion improves cardiac function in adults with type 2 diabetes: a double-blind, placebo-controlled, randomized, crossover trial

Type 2 diabetes (T2D) is a metabolic disease associated with cardiovascular dysfunction. The myocardium preferentially uses ketones over free fatty acids as a more energy-efficient substrate. The primary aim was to assess the effects of ketone monoester (Kme) ingestion on cardiac output index ([Formula: see text]i). The secondary aims were to assess the effects of Kme ingestion on markers of cardiac hemodynamics, muscle oxygenation, and vascular function at rest, during and following step-incremental cycling. We undertook a double-blind, randomized, crossover design study in 13 adults [age, 66 ± 10 yr; body mass index (BMI), 31.3 ± 7.0 kg·m-2] with T2D. Participants completed two conditions, where they ingested a Kme (0.115 g·kg-1) or a placebo taste-matched drink. Cardiac function was measured using thoracic impedance cardiography, and muscle oxygenation of the calf was determined via near-infrared spectroscopy. Macrovascular endothelial function was measured by flow-mediated dilation (FMD), and microvascular endothelial function was measured via transdermal delivery of acetylcholine (ACh) and insulin. Circulating β-hydroxybutyrate [β-Hb] was measured throughout. Kme ingestion raised circulating β-Hb throughout the protocol (peak 1.9 mM; P = 0.001 vs. placebo). Kme ingestion increased [Formula: see text]i by 0.75 ± 0.5 L·min-1·m-2 (P = 0.003), stroke volume index by 7.2 ± 4.5 mL·m-2 (P = 0.001), and peripheral muscle oxygenation by 9.9 ± 7.1% (P = 0.001) and reduced systemic vascular resistance index by -420 ± -225 dyn·s-1·cm-5·m-2 (P = 0.031) compared with the placebo condition. There were no differences between Kme and placebo in heart rate (P = 0.995), FMD (P = 0.542), ACh max (P = 0.800), and insulin max (P = 0.242). Ingestion of Kme improved [Formula: see text], stroke volume index, and peripheral muscle oxygenation but did not alter macro- or microvascular endothelial function in people with T2D.NEW & NOTEWORTHY For the first time, we show that acute ketone monoester ingestion (Kme) can increase cardiac output and stroke volume and reduce systemic vascular resistance at rest and during exercise in sodium glucose transporter inhibitors naïve (i.e. no drug-induced ketosis) people with type 2 diabetes. Acute Kme ingestion improves peripheral skeletal muscle oxygenation during moderate intensity and maximal exercise. Kme has no effect on macro- or microvascular endothelial function in people with type 2 diabetes.

Advancements in nutritional support for critically ill patients

PURPOSE OF REVIEW

To summarize the clinical evidence on nutritional support for critically ill patients, the (patho)physiological mechanisms involved, and areas of future research.

RECENT FINDINGS

Large randomized controlled trials have shown that early nutrition induces dose-dependent harm in critically ill patients, regardless of the feeding route, and that early high-dose amino acids are harmful. Harm has been attributed to feeding-induced suppression of cellular repair pathways including autophagy and ketogenesis, to aggravation of hyperglycemia and insulin needs, and to increased urea cycle activity. Additionally, acute critical illness was shown to be a state of anabolic resistance. The absence of benefit of early enhanced nutritional support on short- and long-term outcomes was observed in all studied subgroups.

SUMMARY

While early high-dose nutrition should be avoided in all critically ill patients, the optimal initiation time of nutrition support for the individual patient, as well as ideal composition and dosing of nutrition over time remain unclear. Future studies should elucidate how fasting-induced repair pathways can be activated while avoiding prolonged starvation, and how hyperglycemia and high insulin need could be prevented. Potential strategies include intermittent fasting, ketogenic diets, ketone supplements, and alternative glucose-lowering agents, whether or not in combination with exercise.

Targeting Ketone Body Metabolism Improves Cardiac Function and Hemodynamics in Patients With Heart Failure: A Systematic Review and Meta-Analysis

CONTEXT

The impacts of elevated ketone body levels on cardiac function and hemodynamics in patients with heart failure (HF) remain unclear.

OBJECTIVE

The effects of ketone intervention on these parameters in patients with HF were evaluated quantitatively in this meta-analysis.

DATA SOURCES

We searched the PubMed, Cochrane Library, and Embase databases for relevant studies published from inception to April 13, 2024. Ketone therapy included ketone ester and β-hydroxybutyrate intervention.

DATA EXTRACTION

Seven human studies were included for the quantitative analysis.

DATA ANALYSIS

Our results showed that ketone therapy significantly improved left ventricular ejection fraction (standardized mean difference, 0.52 [95% CI, 0.25-0.80]; I2 = 0%), cardiac output (0.84 [95% CI, 0.36-1.32]; I2 = 68%) and stroke volume (0.47 [95% CI, 0.10-0.84]; I2 = 39%), and significantly reduced systemic vascular resistance (-0.92 [95% CI, -1.52 to -0.33]; I2 = 74%) without influencing mean arterial pressure (-0.09 [95% CI: -0.40 to 0.22]; I2 = 0%) in patients with HF. Subgroup analysis revealed that the enhanced cardiac function and favorable hemodynamic effects of ketone therapy were also applicable to individuals without HF.

CONCLUSIONS

Ketone therapy may significantly improve cardiac systolic function and hemodynamics in patients with HF and in patients without HF, suggesting it may be a promising treatment for patients with HF and also a beneficial medical strategy for patients without HF or healthy individuals.

Cardiovascular effects of lactate in healthy adults

BACKGROUND

Low-volume hypertonic solutions, such as half-molar lactate (LAC), may be a potential treatment used for fluid resuscitation. This study aimed to evaluate the underlying cardiovascular effects and mechanisms of LAC infusion compared to sodium-matched hypertonic sodium chloride (SAL).

METHODS

Eight healthy male participants were randomized in a controlled, single-blinded, crossover study. Each participant received a four-hour infusion of LAC and SAL in a randomized order. Assessor-blinded echocardiography and blood samples were performed. The primary endpoint was cardiac output (CO) measured by echocardiography.

RESULTS

During LAC infusion, circulating lactate levels increased by 1.9 mmol/L (95% CI 1.8-2.0 mmol/L, P < 0.001) compared with SAL. CO increased by 1.0 L/min (95% CI 0.5-1.4 L/min, P < 0.001), driven primarily by a significant increase in stroke volume of 11 mL (95% CI 4-17 mL, P = 0.002), with no significant change in heart rate. Additionally, left ventricular ejection fraction improved by 5 percentage points (P < 0.001) and global longitudinal strain by 1.5 percentage points (P < 0.001). Preload indicators were elevated during SAL infusion compared with LAC infusion. Concomitantly, afterload parameters, including systemic vascular resistance and effective arterial elastance, were significantly decreased with LAC infusion compared with SAL, while mean arterial pressure remained similar. Indicators of contractility improved during LAC infusion.

CONCLUSIONS

In healthy participants, LAC infusion enhanced cardiac function, evidenced by increases in CO, stroke volume, and left ventricular ejection fraction compared with SAL. Indicators of contractility improved, afterload decreased, and preload remained stable. Therefore, LAC infusion may be an advantageous resuscitation fluid, particularly in patients with cardiac dysfunction.

CLINICAL TRIAL REGISTRATIONS

https://clinicaltrials.gov/ct2/show/NCT04710875 . Registered 1 December 2020.

A murine model of acute and prolonged abdominal sepsis, supported by intensive care, reveals time-dependent metabolic alterations in the heart

BACKGROUND

Sepsis-induced cardiomyopathy (SICM) often occurs in the acute phase of sepsis and is associated with increased mortality due to cardiac dysfunction. The pathogenesis remains poorly understood, and no specific treatments are available. Although SICM is considered reversible, emerging evidence suggests potential long-term sequelae. We hypothesized that metabolic and inflammatory cardiac changes, previously observed in acute sepsis as potential drivers of SICM, partially persist in prolonged sepsis.

METHODS

In 24-week-old C57BL/6J mice, sepsis was induced by cecal ligation and puncture, followed by intravenous fluid resuscitation, subcutaneous analgesics and antibiotics, and, in the prolonged phase, by parenteral nutrition. Mice were killed after 5 days of sepsis (prolonged sepsis, n = 15). For comparison, we included acutely septic mice killed at 30 h (acute sepsis, n = 15) and healthy controls animals (HC, n = 15). Cardiac tissue was collected for assessment of inflammatory and metabolic markers through gene expression, metabolomic analysis and histological assessment.

RESULTS

In prolonged sepsis, cardiac expression of IL-1β and IL-6 and macrophage infiltration remained upregulated (p ≤ 0.05). In contrast, tissue levels of Krebs cycle intermediates and adenosine phosphates were normal, whereas NADPH levels were low in prolonged sepsis (p ≤ 0.05). Gene expression of fatty acid transporters and of the glucose transporter Slc2a1 was upregulated in prolonged sepsis (p ≤ 0.01). Lipid staining and glycogen content were elevated in prolonged sepsis together with increased gene expression of enzymes responsible for lipogenesis and glycogen synthesis (p ≤ 0.05). Intermediate glycolytic metabolites (hexose-phosphates, GADP, DHAP) were elevated (p ≤ 0.05), but gene expression of several enzymes for glycolysis and mitochondrial oxidation of pyruvate, fatty-acyl-CoA and ketone bodies to acetyl-CoA were suppressed in prolonged sepsis (p ≤ 0.05). Key metabolic transcription factors PPARα and PGC-1α were downregulated in acute, but upregulated in prolonged, sepsis (p ≤ 0.05 for both). Ketone body concentrations were normal but ketolytic enzymes remained suppressed (p ≤ 0.05). Amino acid metabolism showed mild, mixed changes.

CONCLUSIONS

Our results suggest myocardial lipid and glycogen accumulation and suppressed mitochondrial oxidation, with a functionally intact Krebs cycle, in the prolonged phase of sepsis, together with ongoing myocardial inflammation. Whether these alterations have functional consequences and predispose to long-term sequelae of SICM needs further research.

Cardiovascular and Metabolic Effects of Modulating Circulating Ketone Bodies With 1,3-Butanediol in Patients With Heart Failure With Reduced Ejection Fraction

BACKGROUND

Oral treatment with the exogenous ketone body 3-hydroxybutyrate improves cardiac function in patients with heart failure with reduced ejection fraction, but ketosis is limited to 3 to 4 hours. Treatment with (R)-1,3-butanediol (BD) provides prolonged ketosis in healthy controls, but the hemodynamic and metabolic profile is unexplored in patients with heart failure with reduced ejection fraction.

METHODS AND RESULTS

This was a randomized, single-blind, placebo-controlled, crossover study. Transthoracic echocardiography and venous blood samples were performed at baseline and hourly for 6 hours after an oral dose of BD (0.5 g/kg) or taste-matched placebo. The primary end point was the average between-treatment difference in cardiac output during the 6-hour period after intake. Secondary end points were stroke volume, heart rate, left ventricular ejection fraction, circulating 3-hydroxybutyrate, and free fatty acids. Twelve patients with heart failure with reduced ejection fraction were included. BD treatment provided significant increase in circulating 3-hydroxybutyrate by 1400 μmol/L (95% CI, 1262-1538 μmol/L, P<0.001) and increased cardiac output by 0.9 L/min (95% CI, 0.7-1.1 L/min, P<0.001) compared with placebo. Stroke volume increased by 15 mL (95% CI, 11-19 mL, P<0.001), and heart rate remained similar between treatments (P=0.150). Left ventricular ejection fraction increased by 3 percentage points (95% CI, 1-4 percentage points, P<0.001). Global longitudinal strain improved (P<0.001). Left ventricular contractility estimates increased after BD intake, and parameters of afterload were reduced. Finally, free fatty acids and glucose levels decreased.

CONCLUSIONS

Oral dosing of BD led to prolonged ketosis and cardiovascular and metabolic benefits in patients with heart failure with reduced ejection fraction. Treatment with BD is an attractive option to achieve beneficial effects from sustained therapeutic ketosis.

REGISTRATION

URL: https://www.clinicaltrials.gov; Unique identifier: NCT05768100.

Effect of Hyperketonemia on Myocardial Function in Patients With Heart Failure and Type 2 Diabetes

We examined the effect of increased levels of plasma ketones on left ventricular (LV) function, myocardial glucose uptake (MGU), and myocardial blood flow (MBF) in patients with type 2 diabetes (T2DM) with heart failure. Three groups of patients with T2DM (n = 12 per group) with an LV ejection fraction (EF) ≤50% received incremental infusions of β-hydroxybutyrate (β-OH-B) for 3-6 h to increase the plasma β-OH-B concentration throughout the physiologic (groups I and II) and pharmacologic (group III) range. Cardiac MRI was performed at baseline and after each β-OH-B infusion to provide measures of cardiac function. On a separate day, group II also received a sodium bicarbonate (NaHCO3) infusion, thus serving as their own control for time, volume, and pH. Additionally, group II underwent positron emission tomography study with 18F-fluoro-2-deoxyglucose to examine effect of hyperketonemia on MGU. Groups I, II, and III achieved plasma β-OH-B levels (mean ± SEM) of 0.7 ± 0.3, 1.6 ± 0.2, 3.2 ± 0.2 mmol/L, respectively. Cardiac output (CO), LVEF, and stroke volume (SV) increased significantly during β-OH-B infusion in groups II (CO, from 4.54 to 5.30; EF, 39.9 to 43.8; SV, 70.3 to 80.0) and III (CO, from 5.93 to 7.16; EF, 41.1 to 47.5; SV, 89.0 to 108.4), and did not change with NaHCO3 infusion in group II. The increase in LVEF was greatest in group III (P < 0.001 vs. group II). MGU and MBF were not altered by β-OH-B. In patients with T2DM and LVEF ≤50%, increased plasma β-OH-B level significantly increased LV function dose dependently. Because MGU did not change, the myocardial benefit of β-OH-B resulted from providing an additional fuel for the heart without inhibiting MGU.

ARTICLE HIGHLIGHTS

Acetyltransferase in cardiovascular disease and aging

Acetyltransferases are enzymes that catalyze the transfer of an acetyl group to a substrate, a modification referred to as acetylation. Loss-of-function variants in genes encoding acetyltransferases can lead to congenital disorders, often characterized by intellectual disability and heart and muscle defects. Their activity is influenced by dietary nutrients that alter acetyl coenzyme A levels, a key cofactor. Cardiovascular diseases, including ischemic, hypertensive, and diabetic heart diseases - leading causes of mortality in the elderly - are largely attributed to prolonged lifespan and the growing prevalence of metabolic syndrome. Acetyltransferases thus serve as a crucial link between lifestyle modifications, cardiometabolic disease, and aging through both epigenomic and non-epigenomic mechanisms. In this review, we discuss the roles and relevance of acetyltransferases. While the sirtuin family of deacetylases has been extensively studied in longevity, particularly through fasting-mediated NAD+ metabolism, recent research has brought attention to the essential roles of acetyltransferases in health and aging-related pathways, including cell proliferation, DNA damage response, mitochondrial function, inflammation, and senescence. We begin with an overview of acetyltransferases, classifying them by domain structure, including canonical and non-canonical lysine acetyltransferases, N-terminal acetyltransferases, and sialic acid O-acetyltransferases. We then discuss recent advances in understanding acetyltransferase-related pathologies, particularly focusing on cardiovascular disease and aging, and explore their potential therapeutic applications for promoting health in older individuals.

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.

Leveraging metabolism for better outcomes in heart failure

Whilst metabolic inflexibility and substrate constraint have been observed in heart failure for many years, their exact causal role remains controversial. In parallel, many of our fundamental assumptions about cardiac fuel use are now being challenged like never before. For example, the emergence of sodium-glucose cotransporter 2 inhibitor therapy as one of the four 'pillars' of heart failure therapy is causing a revisit of metabolism as a key mechanism and therapeutic target in heart failure. Improvements in the field of cardiac metabolomics will lead to a far more granular understanding of the mechanisms underpinning normal and abnormal human cardiac fuel use, an appreciation of drug action, and novel therapeutic strategies. Technological advances and expanding biorepositories offer exciting opportunities to elucidate the novel aspects of these metabolic mechanisms. Methodologic advances include comprehensive and accurate substrate quantitation such as metabolomics and stable-isotope fluxomics, improved access to arterio-venous blood samples across the heart to determine fuel consumption and energy conversion, high quality cardiac tissue biopsies, biochemical analytics, and informatics. Pairing these technologies with recent discoveries in epigenetic regulation, mitochondrial dynamics, and organ-microbiome metabolic crosstalk will garner critical mechanistic insights in heart failure. In this state-of-the-art review, we focus on new metabolic insights, with an eye on emerging metabolic strategies for heart failure. Our synthesis of the field will be valuable for a diverse audience with an interest in cardiac metabolism.

Cardiogenic shock

Cardiogenic shock is a complex syndrome defined by systemic hypoperfusion and inadequate cardiac output arising from a wide array of underlying causes. Although the understanding of cardiogenic shock epidemiology, specific subphenotypes, haemodynamics, and cardiogenic shock severity staging has evolved, few therapeutic interventions have shown survival benefit. Results from seminal randomised controlled trials support early revascularisation of the culprit vessel in infarct-related cardiogenic shock and provide evidence of improved survival with the use of temporary circulatory support in selected patients. However, numerous questions remain unanswered, including optimal pharmacotherapy regimens, the role of mechanical circulatory support devices, management of secondary organ dysfunction, and best supportive care. This Review summarises current definitions, pathophysiological principles, and management approaches in cardiogenic shock, and highlights key knowledge gaps to advance individualised shock therapy and the evidence-based ethical use of modern technology and resources in cardiogenic shock.

Randomized Crossover Trial of 2-Week Ketone Ester Treatment in Patients With Type 2 Diabetes and Heart Failure With Preserved Ejection Fraction

BACKGROUND

Heart failure with preserved ejection fraction (HFpEF) is a major cause of morbidity and mortality in patients with type 2 diabetes (T2D). Acute increases in circulating levels of ketone body 3-hydroxybutyrate have beneficial acute hemodynamic effects in patients without T2D with chronic heart failure with reduced ejection fraction. However, the cardiovascular effects of prolonged oral ketone ester (KE) treatment in patients with T2D and HFpEF remain unknown.

METHODS

A total of 24 patients with T2D and HFpEF completed a 6-week randomized, double-blind crossover study. All patients received 2 weeks of KE treatment (25 g D-ß-hydroxybutyrate-(R)-1,3-butanediol × 4 daily) and isocaloric and isovolumic placebo, separated by a 2-week washout period. At the end of each treatment period, patients underwent right heart catheterization, echocardiography, and blood samples at trough levels of intervention, and then during a 4-hour resting period after a single dose. A subsequent second dose was administered, followed by an exercise test. The primary end point was cardiac output during the 4-hour rest period.

RESULTS

During the 4-hour resting period, circulating 3-hydroxybutyrate levels were 10-fold higher after KE treatment (1010±56 µmol/L; P<0.001) compared with placebo (91±55 µmol/L). Compared with placebo, KE treatment increased cardiac output by 0.2 L/min (95% CI, 0.1 to 0.3) during the 4-hour period and decreased pulmonary capillary wedge pressure at rest by 1 mm Hg (95% CI, -2 to 0) and at peak exercise by 5 mm Hg (95% CI, -9 to -1). KE treatment decreased the pressure-flow relationship (∆ pulmonary capillary wedge pressure/∆ cardiac output) significantly during exercise (P<0.001) and increased stroke volume by 10 mL (95% CI, 0 to 20) at peak exercise. KE right-shifted the left ventricular end-diastolic pressure-volume relationship, suggestive of reduced left ventricular stiffness and improved compliance. Favorable hemodynamic responses of KE treatment were also observed in patients treated with sodium-glucose transporter-2 inhibitors and glucagon-like peptide-1 analogs.

CONCLUSIONS

In patients with T2D and HFpEF, a 2-week oral KE treatment increased cardiac output and reduced cardiac filling pressures and ventricular stiffness. At peak exercise, KE treatment markedly decreased pulmonary capillary wedge pressure and improved pressure-flow relationship. Modulation of circulating ketone levels is a potential new treatment modality for patients with T2D and HFpEF.

REGISTRATION

URL: https://www.clinicaltrials.gov; Unique Identifier: NCT05236335.

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

BACKGROUND

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

OBJECTIVE

The purpose of this study was to evaluate the associations of circulating KB levels with incident AF risk in the general population.

METHODS

We studied 237,163 participants [mean age, 56.5 years; 129,472 women (55%)] from the UK Biobank who were free of AF at baseline and had data on circulating β-hydroxybutyrate (β-OHB), acetoacetate, and acetone. The associations of KBs with new-onset AF were evaluated using Cox regression in the general population and across the 3 genetic risk groups: low, moderate, and high polygenic risk score of AF.

RESULTS

During a median follow-up of 14.8 (13.8, 15.5) years, 16,638 participants (7.0%) developed AF. There was a U-shaped association of total KBs and β-OHB with incident AF, with nadirs at 60.6 and 40.8 μmol/L, respectively (Pnonlinear < .05), whereas there was a positive association of acetoacetate and acetone with AF (Poverall < .001; Pnonlinear > .05). Consistently, there was a U-shaped association of total KBs and β-OHB with left atrial (LA) volume parameters, including LA maximum volume, LA minimum volume, and their body surface area-indexed counterparts, and there was an inverted U-shaped association of total KBs and β-OHB with LA ejection fraction (Pnonlinear < .05 for all). The associations of KBs with AF were stronger in individuals with low genetic risk (Pinteraction < .05), while the highest AF risk was in those with high genetic risk with high KB levels. Significant mediation effects of inflammatory markers on the associations between KBs and AF were identified.

CONCLUSION

There was a U-shaped association of circulating total KBs and β-OHB with incident AF as well as a positive association of acetoacetate and acetone levels with AF risk in the general population.

Preparation and Preclinical Characterization of a Simple Ester for Dual Exogenous Supply of Lactate and Beta-hydroxybutyrate

Elevation of the plasma levels of (S)-lactate (Lac) and/or (R)-beta-hydroxybutyrate (BHB) occurs naturally in response to strenuous exercise and prolonged fasting, respectively, resulting in millimolar concentrations of these two metabolites. It is increasingly appreciated that Lac and BHB have wide-ranging beneficial physiological effects, suggesting that novel nutritional solutions, compatible with high-level and/or sustained consumption, which allow direct control of plasma levels of Lac and BHB, are of strong interest. In this study, we present a molecular hybrid between (S)-lactate and the BHB-precursor (R)-1,3-butanediol in the form of a simple ester referred to as LaKe. We show that LaKe can be readily prepared on the kilogram scale and undergoes rapid hydrolytic conversion under a variety of physiological conditions to release its two constituents. Oral ingestion of LaKe, in rats, resulted in dose-dependent elevation of plasma levels of Lac and BHB triggering expected physiological responses such as reduced lipolysis and elevation of the appetite-suppressing compound N-L-lactoyl-phenylalanine (Lac-Phe).

Obesity and Weight Loss Strategies for Patients With Heart Failure

Obesity is a common comorbidity among patients with heart failure with reduced ejection fraction (HFrEF) or heart failure with preserved ejection fraction (HFpEF), with the strongest pathophysiologic link of obesity being seen for HFpEF. Lifestyle measures are the cornerstone of weight loss management, but sustainability is a challenge, and there are limited efficacy data in the heart failure (HF) population. Bariatric surgery has moderate efficacy and safety data for patients with preoperative HF or left ventricular dysfunction and has been associated with reductions in HF hospitalizations and medium-term mortality. Antiobesity medications historically carried concerns for cardiovascular adverse effects, but the safety and weight loss efficacy seen in general population trials of glucagon-like peptide 1 (GLP-1) and gastric inhibitory polypeptide/GLP-1 agonists are highly encouraging. Although there are safety concerns regarding GLP-1 agonists in advanced HFrEF, trials of the GLP-1 agonist semaglutide for treatment of obesity have confirmed safety and efficacy in patients with HFpEF.

β-hydroxybutyrate and ischemic stroke: roles and mechanisms

Stroke is a significant global burden, causing extensive morbidity and mortality. In metabolic states where glucose is limited, ketone bodies, predominantly β-hydroxybutyrate (BHB), act as alternative fuel sources. Elevated levels of BHB have been found in the ischemic hemispheres of animal models of stroke, supporting its role in the pathophysiology of cerebral ischemia. Clinically, higher serum and urinary BHB concentrations have been associated with adverse outcomes in ischemic stroke, highlighting its potential utility as a prognostic biomarker. In both animal and cellular models, exogenous BHB administration has exhibited neuroprotective effects, reduction of infarct size, and improvement of neurological outcomes. In this review, we focus on the role of BHB before and after ischemic stroke, with an emphasis on the therapeutic potential and mechanisms of ketone administration after ischemic stroke.

Cardiovascular Effects of Oral Ketone Ester Treatment in Patients With Heart Failure With Reduced Ejection Fraction: A Randomized, Controlled, Double-Blind Trial

BACKGROUND

Heart failure triggers a shift in myocardial metabolic substrate utilization, favoring the ketone body 3-hydroxybutyrate as energy source. We hypothesized that 14-day treatment with ketone ester (KE) would improve resting and exercise hemodynamics and exercise capacity in patients with heart failure with reduced ejection fraction.

METHODS

In a randomized, double-blind cross-over study, nondiabetic patients with heart failure with reduced ejection fraction received 14-day KE and 14-day isocaloric non-KE comparator regimens of 4 daily doses separated by a 14-day washout period. After each treatment period, participants underwent right heart catheterization, echocardiography, and blood sampling at plasma trough levels and after dosing. Participants underwent an exercise hemodynamic assessment after a second dosing. The primary end point was resting cardiac output (CO). Secondary end points included resting and exercise pulmonary capillary wedge pressure and peak exercise CO and metabolic equivalents.

RESULTS

We included 24 patients with heart failure with reduced ejection fraction (17 men; 65±9 years of age; all White). Resting CO at trough levels was higher after KE compared with isocaloric comparator (5.2±1.1 L/min versus 5.0±1.1 L/min; difference, 0.3 L/min [95% CI, 0.1-0.5), and pulmonary capillary wedge pressure was lower (8±3 mm Hg versus 11±3 mm Hg; difference, -2 mm Hg [95% CI, -4 to -1]). These changes were amplified after KE dosing. Across all exercise intensities, KE treatment was associated with lower mean exercise pulmonary capillary wedge pressure (-3 mm Hg [95% CI, -5 to -1] ) and higher mean CO (0.5 L/min [95% CI, 0.1-0.8]), significantly different at low to moderate steady-state exercise but not at peak. Metabolic equivalents remained similar between treatments. In exploratory analyses, KE treatment was associated with 18% lower NT-proBNP (N-terminal pro-B-type natriuretic peptide; difference, -98 ng/L [95% CI, -185 to -23]), higher left ventricular ejection fraction (37±5 versus 34±5%; P=0.01), and lower left atrial and ventricular volumes.

CONCLUSIONS

KE treatment for 14 days was associated with higher CO at rest and lower filling pressures, cardiac volumes, and NT-proBNP levels compared with isocaloric comparator. These changes persisted during exercise and were achieved on top of optimal medical therapy. Sustained modulation of circulating ketone bodies is a potential treatment principle in patients with heart failure with reduced ejection fraction.

REGISTRATION

URL: https://www.clinicaltrials.gov; Unique identifier: NCT05161650.

Lipotoxicity as a therapeutic target in obesity and diabetic cardiomyopathy

Unhealthy sources of fats, ultra-processed foods with added sugars, and a sedentary lifestyle make humans more susceptible to developing overweight and obesity. While lipids constitute an integral component of the organism, excessive and abnormal lipid accumulation that exceeds the storage capacity of lipid droplets disrupts the intracellular composition of fatty acids and results in the release of deleterious lipid species, thereby giving rise to a pathological state termed lipotoxicity. This condition induces endoplasmic reticulum stress, mitochondrial dysfunction, inflammatory responses, and cell death. Recent advances in omics technologies and analytical methodologies and clinical research have provided novel insights into the mechanisms of lipotoxicity, including gut dysbiosis, epigenetic and epitranscriptomic modifications, dysfunction of lipid droplets, post-translational modifications, and altered membrane lipid composition. In this review, we discuss the recent knowledge on the mechanisms underlying the development of lipotoxicity and lipotoxic cardiometabolic disease in obesity, with a particular focus on lipotoxic and diabetic cardiomyopathy.

Enantiomer-Specific Cardiovascular Effects of the Ketone Body 3-Hydroxybutyrate

BACKGROUND

The ketone body 3-hydroxybutyrate (3-OHB) increases cardiac output (CO) by 35% to 40% in healthy people and people with heart failure. The mechanisms underlying the effects of 3-OHB on myocardial contractility and loading conditions as well as the cardiovascular effects of its enantiomeric forms, D-3-OHB and L-3-OHB, remain undetermined.

METHODS AND RESULTS

Three groups of 8 pigs each underwent a randomized, crossover study. The groups received 3-hour infusions of either D/L-3-OHB (racemic mixture), 100% L-3-OHB, 100% D-3-OHB, versus an isovolumic control. The animals were monitored with pulmonary artery catheter, left ventricle pressure-volume catheter, and arterial and coronary sinus blood samples. Myocardial biopsies were evaluated with high-resolution respirometry, coronary arteries with isometric myography, and myocardial kinetics with D-[11C]3-OHB and L-[11C]3-OHB positron emission tomography. All three 3-OHB infusions increased 3-OHB levels (P<0.001). D/L-3-OHB and L-3-OHB increased CO by 2.7 L/min (P<0.003). D-3-OHB increased CO nonsignificantly (P=0.2). Circulating 3-OHB levels correlated with CO for both enantiomers (P<0.001). The CO increase was mediated through arterial elastance (afterload) reduction, whereas contractility and preload were unchanged. Ex vivo, D- and L-3-OHB dilated coronary arteries equally. The mitochondrial respiratory capacity remained unaffected. The myocardial 3-OHB extraction increased only during the D- and D/L-3-OHB infusions. D-[11C]3-OHB showed rapid cardiac uptake and metabolism, whereas L-[11C]3-OHB demonstrated much slower pharmacokinetics.

CONCLUSIONS

3-OHB increased CO by reducing afterload. L-3-OHB exerted a stronger hemodynamic response than D-3-OHB due to higher circulating 3-OHB levels. There was a dissocitation between the myocardial metabolism and hemodynamic effects of the enantiomers, highlighting L-3-OHB as a potent cardiovascular agent with strong hemodynamic effects.

Lactate infusion elevates cardiac output through increased heart rate and decreased vascular resistance: a randomised, blinded, crossover trial in a healthy porcine model

BACKGROUND

Lactate is traditionally recognized as a by-product of anaerobic metabolism. However, lactate is a preferred oxidative substrate for stressed myocardium. Exogenous lactate infusion increases cardiac output (CO). The exact mechanism underlying this mechanism has yet to be elucidated. The aim of this study was to investigate the cardiovascular mechanisms underlying the acute haemodynamic effects of exogenous lactate infusion in an experimental model of human-sized pigs.

METHODS

In this randomised, blinded crossover study in eight 60-kg-pigs, the pigs received infusions with one molar sodium lactate and a control infusion of tonicity matched hypertonic saline in random order. We measured CO and pulmonary pressures using a pulmonary artery catheter. A pressure-volume admittance catheter in the left ventricle was used to measure contractility, afterload, preload and work-related parameters.

RESULTS

Lactate infusion increased circulating lactate levels by 9.9 mmol/L (95% confidence interval (CI) 9.1 to 11.0) and CO by 2.0 L/min (95% CI 1.2 to 2.7). Afterload decreased as arterial elastance fell by  -1.0 mmHg/ml (95% CI  -2.0 to  -0.1) and systemic vascular resistance decreased by  -548 dynes/s/cm5 (95% CI  -261 to  -835). Mixed venous saturation increased by 11 percentage points (95% CI 6 to 16), whereas ejection fraction increased by 16.0 percentage points (95% CI 1.1 to 32.0) and heart rate by 21 bpm (95% CI 8 to 33). No significant changes in contractility nor preload were observed.

CONCLUSION

Lactate infusion increased cardiac output by increasing heart rate and lowering afterload. No differences were observed in left ventricular contractility or preload. Lactate holds potential as a treatment in situations with lowered CO and should be investigated in future clinical studies.

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.

Metabolic adaptations in pressure overload hypertrophic heart

This review article offers a detailed examination of metabolic adaptations in pressure overload hypertrophic hearts, a condition that plays a pivotal role in the progression of heart failure with preserved ejection fraction (HFpEF) to heart failure with reduced ejection fraction (HFrEF). The paper delves into the complex interplay between various metabolic pathways, including glucose metabolism, fatty acid metabolism, branched-chain amino acid metabolism, and ketone body metabolism. In-depth insights into the shifts in substrate utilization, the role of different transporter proteins, and the potential impact of hypoxia-induced injuries are discussed. Furthermore, potential therapeutic targets and strategies that could minimize myocardial injury and promote cardiac recovery in the context of pressure overload hypertrophy (POH) are examined. This work aims to contribute to a better understanding of metabolic adaptations in POH, highlighting the need for further research on potential therapeutic applications.

Metabolic Messengers: ketone bodies

Prospective molecular targets and therapeutic applications for ketone body metabolism have increased exponentially in the past decade. Initially considered to be restricted in scope as liver-derived alternative fuel sources during periods of carbohydrate restriction or as toxic mediators during diabetic ketotic states, ketogenesis and ketone bodies modulate cellular homeostasis in multiple physiological states through a diversity of mechanisms. Selective signalling functions also complement the metabolic fates of the ketone bodies acetoacetate and D-β-hydroxybutyrate. Here we discuss recent discoveries revealing the pleiotropic roles of ketone bodies, their endogenous sourcing, signalling mechanisms and impact on target organs, and considerations for when they are either stimulated for endogenous production by diets or pharmacological agents or administered as exogenous wellness-promoting agents.

Comparative Metabolomics in Single Ventricle Patients after Fontan Palliation: A Strong Case for a Targeted Metabolic Therapy

Most studies on single ventricle (SV) circulation take a physiological or anatomical approach. Although there is a tight coupling between cardiac contractility and metabolism, the metabolic perspective on this patient population is very recent. Early findings point to major metabolic disturbances, with both impaired glucose and fatty acid oxidation in the cardiomyocytes. Additionally, Fontan patients have systemic metabolic derangements such as abnormal glucose metabolism and hypocholesterolemia. Our literature review compares the metabolism of patients with a SV circulation after Fontan palliation with that of patients with a healthy biventricular (BV) heart, or different subtypes of a failing BV heart, by Pubmed review of the literature on cardiac metabolism, Fontan failure, heart failure (HF), ketosis, metabolism published in English from 1939 to 2023. Early evidence demonstrates that SV circulation is not only a hemodynamic burden requiring staged palliation, but also a metabolic issue with alterations similar to what is known for HF in a BV circulation. Alterations of fatty acid and glucose oxidation were found, resulting in metabolic instability and impaired energy production. As reported for patients with BV HF, stimulating ketone oxidation may be an effective treatment strategy for HF in these patients. Few but promising clinical trials have been conducted thus far to evaluate therapeutic ketosis with HF using a variety of instruments, including ketogenic diet, ketone esters, and sodium-glucose co-transporter-2 (SGLT2) inhibitors. An initial trial on a small cohort demonstrated favorable outcomes for Fontan patients treated with SGLT2 inhibitors. Therapeutic ketosis is worth considering in the treatment of Fontan patients, as ketones positively affect not only the myocardial energy metabolism, but also the global Fontan physiopathology. Induced ketosis seems promising as a concerted therapeutic strategy.