Ketone ester supplementation suppresses cardiac inflammation and improves cardiac energetics in a swine model of acute myocardial infarction.

BACKGROUND: Myocardial infarction (MI) is a major risk factor for the development of heart failure with reduce ejection fraction (HFrEF). While previous studies have focused on HFrEF, the cardiovascular effects of ketone bodies in acute MI are unclear. We examined the effects of oral ketone supplementation as a potential treatment strategy in a swine acute MI model. METHODS: Farm pigs underwent percutaneous balloon occlusion of the LAD for 80 min followed by 72 h reperfusion period. Oral ketone ester or vehicle was administered during reperfusion and continued during the follow-up period. RESULTS: Oral KE supplementation induced ketonemia 2-3 mmol/l within 30 min after ingestion. KE increased ketone (ßHB) extraction in healthy hearts without affecting glucose and fatty acid (FA) consumption. During reperfusion, the MI hearts consumed less FA with no change in glucose consumption, whereas hearts from MI-KE-fed animals consumed more ßHB and FA, as well as improved myocardial ATP production. A significant elevation of infarct T2 values indicative of inflammation was found only in untreated MI group compared to sham. Concordantly, cardiac expression of inflammatory markers, oxidative stress, and apoptosis were reduced by KE. RNA-seq analysis identified differentially expressed genes related to mitochondrial energy metabolism and inflammation. CONCLUSIONS: Oral KE supplementation induced ketosis and enhanced myocardial ßHB extraction in both healthy and infarcted hearts. Acute oral supplementation with KE favorably altered cardiac substrate uptake and utilization, improved cardiac ATP levels, and reduced cardiac inflammation following MI.

Contrast-Enhanced Cardiac Magnetic Resonance Imaging With a Manganese-Based Alternative to Gadolinium for Tissue Characterization of Acute Myocardial Infarction.

Background Late gadolinium enhancement cardiac magnetic resonance imaging is an effective and reproducible method for characterizing myocardial infarction. However, gadolinium-based contrast agents are contraindicated in patients with acute and chronic renal insufficiency. In addition, several recent studies have noted tissue deposition of free gadolinium in patients who have undergone serial contrast-enhanced magnetic resonance imaging. There is a clinical need for alternative forms of magnetic resonance imaging contrast agents that are acceptable in the setting of renal insufficiency. Methods and Results Three days after 80 minutes of ischemia/reperfusion of the left anterior descending coronary artery, cardiac magnetic resonance imaging was performed to assess myocardial lesion burden using both contrast agents. Late gadolinium enhancement cardiac magnetic resonance imaging was examined 10 and 15 minutes after contrast injection. Contrast agents were administered in alternating manner with a 2- to 3-hour washout period between contrast agent injections. Lesion evaluation and image processing were performed using Segment Medviso software. Mean infarct size and transmurality, measured using RVP-001, were not different compared with those measured using late gadolinium enhancement images. Bland-Altman analysis demonstrated a nominal bias of 0.13 mL (<1% of average total lesion volume) for RVP-001 in terms of gross infarct size measurement. Conclusions The experimental manganese-based contrast agent RVP-001 appears to be an effective agent for assessment of myocardial infarction location, size, and transmurality, and it may be useful as an alternative to gadolinium-based agents.

Mapping the Unseen: In Vivo CEST-MRI of Creatine Reveals Improved Cardiac Energetics in Subjects with Obesity Following Bariatric Surgery.

BACKGROUND: Obesity is associated with derangement of cardiac metabolism and the development of subclinical cardiovascular disease. This prospective study examined the impact of bariatric surgery on cardiac function and metabolism. METHODS: Subjects with obesity underwent cardiac magnetic resonance imaging (CMR) at Massachusetts General Hospital before and after bariatric surgery between 2019 and 2021. The imaging protocol included Cine for global cardiac function assessment and creatine chemical exchange saturation transfer (CEST) CMR for myocardial creatine mapping. RESULTS: Thirteen subjects were enrolled, and 6 subjects [mean BMI 40.5 ± 2.6] had completed the second CMR (i.e. post-surgery), with a median follow-up of 10 months. The median age was 46.5 years, 67% were female, and 16.67% had diabetes. Bariatric surgery led to significant weight loss, with achieved mean BMI of 31.0 ± 2.0. Additionally, bariatric surgery resulted in significant reduction in left ventricular (LV) mass, LV mass index, and epicardial adipose tissue (EAT) volume. This was accompanied by slight improvement in LV ejection fraction compared to baseline. Following bariatric surgery, there was a significant increase in creatine CEST contrast. Subjects with obesity had significantly lower CEST contrast compared to subjects with normal BMI (n = 10), but this contrast was normalized after the surgery, and statistically similar to non-obese cohort, indicating an improvement in myocardial energetics. CONCLUSIONS: CEST-CMR has the ability to identify and characterize myocardial metabolism in vivo non-invasively. These results demonstrate that in addition to reducing BMI, bariatric surgery may favorably affect cardiac function and metabolism.

Magnetic resonance imaging of cardiac metabolism in heart failure: how far have we come?

As one of the highest energy consumer organs in the body, the heart requires tremendous amount of adenosine triphosphate (ATP) to maintain its continuous mechanical work. Fatty acids, glucose, and ketone bodies are the primary fuel source of the heart to generate ATP with perturbations in ATP generation possibly leading to contractile dysfunction. Cardiac metabolic imaging with magnetic resonance imaging (MRI) plays a crucial role in understanding the dynamic metabolic changes occurring in the failing heart, where the cardiac metabolism is deranged. Also, targeting and quantifying metabolic changes in vivo noninvasively is a promising approach to facilitate diagnosis, determine prognosis, and evaluate therapeutic response. Here, we summarize novel MRI techniques used for detailed investigation of cardiac metabolism in heart failure including magnetic resonance spectroscopy (MRS), hyperpolarized MRS, and chemical exchange saturation transfer based on evidence from preclinical and clinical studies and to discuss the potential clinical application in heart failure.

Exercise-induced CITED4 expression is necessary for regional remodeling of cardiac microstructural tissue helicity.

Both exercise-induced molecular mechanisms and physiological cardiac remodeling have been previously studied on a whole heart level. However, the regional microstructural tissue effects of these molecular mechanisms in the heart have yet to be spatially linked and further elucidated. We show in exercised mice that the expression of CITED4, a transcriptional co-regulator necessary for cardioprotection, is regionally heterogenous in the heart with preferential significant increases in the lateral wall compared with sedentary mice. Concordantly in this same region, the heart's local microstructural tissue helicity is also selectively increased in exercised mice. Quantification of CITED4 expression and microstructural tissue helicity reveals a significant correlation across both sedentary and exercise mouse cohorts. Furthermore, genetic deletion of CITED4 in the heart prohibits regional exercise-induced microstructural helicity remodeling. Taken together, CITED4 expression is necessary for exercise-induced regional remodeling of the heart's microstructural helicity revealing how a key molecular regulator of cardiac remodeling manifests into downstream local tissue-level changes.

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.

SGLT2 Inhibitors and Ketone Metabolism in Heart Failure.

Sodium-glucose cotransporter-2 (SGLT2) inhibitors have emerged as powerful drugs that can be used to treat heart failure (HF) patients, both with preserved and reduced ejection fraction and in the presence or absence of type 2 diabetes. While the mechanisms underlying the salutary effects of SGLT2 inhibitors have not been fully elucidated, there is clear evidence for a beneficial metabolic effect of these drugs. In this review, we discuss the effects of SGLT2 inhibitors on cardiac energy provision secondary to ketone bodies, pathological ventricular remodeling, and inflammation in patients with HF. While the specific contribution of ketone bodies to the pleiotropic cardiovascular benefits of SGLT2 inhibitors requires further clarification, ketone bodies themselves may also be used as a therapy for HF.

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.

The erythropoietin receptor expressed in skeletal muscle is essential for mitochondrial biogenesis and physiological exercise.

Erythropoietin (EPO) is a haematopoietic hormone that regulates erythropoiesis, but the EPO-receptor (EpoR) is also expressed in non-haematopoietic tissues. Stimulation of the EpoR in cardiac and skeletal muscle provides protection from various forms of pathological stress, but its relevance for normal muscle physiology remains unclear. We aimed to determine the contribution of the tissue-specific EpoR to exercise-induced remodelling of cardiac and skeletal muscle. Baseline phenotyping was performed on left ventricle and m. gastrocnemius of mice that only express the EpoR in haematopoietic tissues (EpoR-tKO). Subsequently, mice were caged in the presence or absence of a running wheel for 4 weeks and exercise performance, cardiac function and histological and molecular markers for physiological adaptation were assessed. While gross morphology of both muscles was normal in EpoR-tKO mice, mitochondrial content in skeletal muscle was decreased by 50%, associated with similar reductions in mitochondrial biogenesis, while mitophagy was unaltered. When subjected to exercise, EpoR-tKO mice ran slower and covered less distance than wild-type (WT) mice (5.5 ± 0.6 vs. 8.0 ± 0.4 km/day, p < 0.01). The impaired exercise performance was paralleled by reductions in myocyte growth and angiogenesis in both muscle types. Our findings indicate that the endogenous EPO-EpoR system controls mitochondrial biogenesis in skeletal muscle. The reductions in mitochondrial content were associated with reduced exercise capacity in response to voluntary exercise, supporting a critical role for the extra-haematopoietic EpoR in exercise performance.

ATPase Inhibitory Factor-1 Disrupts Mitochondrial Ca2+ Handling and Promotes Pathological Cardiac Hypertrophy through CaMKIIδ.

ATPase inhibitory factor-1 (IF1) preserves cellular ATP under conditions of respiratory collapse, yet the function of IF1 under normal respiring conditions is unresolved. We tested the hypothesis that IF1 promotes mitochondrial dysfunction and pathological cardiomyocyte hypertrophy in the context of heart failure (HF). Methods and results: Cardiac expression of IF1 was increased in mice and in humans with HF, downstream of neurohumoral signaling pathways and in patterns that resembled the fetal-like gene program. Adenoviral expression of wild-type IF1 in primary cardiomyocytes resulted in pathological hypertrophy and metabolic remodeling as evidenced by enhanced mitochondrial oxidative stress, reduced mitochondrial respiratory capacity, and the augmentation of extramitochondrial glycolysis. Similar perturbations were observed with an IF1 mutant incapable of binding to ATP synthase (E55A mutation), an indication that these effects occurred independent of binding to ATP synthase. Instead, IF1 promoted mitochondrial fragmentation and compromised mitochondrial Ca2+ handling, which resulted in sarcoplasmic reticulum Ca2+ overloading. The effects of IF1 on Ca2+ handling were associated with the cytosolic activation of calcium-calmodulin kinase II (CaMKII) and inhibition of CaMKII or co-expression of catalytically dead CaMKIIδC was sufficient to prevent IF1 induced pathological hypertrophy. Conclusions: IF1 represents a novel member of the fetal-like gene program that contributes to mitochondrial dysfunction and pathological cardiac remodeling in HF. Furthermore, we present evidence for a novel, ATP-synthase-independent, role for IF1 in mitochondrial Ca2+ handling and mitochondrial-to-nuclear crosstalk involving CaMKII.

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.

Factor Xa Inhibition with Apixaban Does Not Influence Cardiac Remodelling in Rats with Heart Failure After Myocardial Infarction.

BACKGROUND: Heart failure (HF) is considered to be a prothrombotic condition and it has been suggested that coagulation factors contribute to maladaptive cardiac remodelling via activation of the protease-activated receptor 1 (PAR1). We tested the hypothesis that anticoagulation with the factor Xa (FXa) inhibitor apixaban would ameliorate cardiac remodelling in rats with HF after myocardial infarction (MI). METHODS AND RESULTS: Male Sprague-Dawley rats were either subjected to permanent ligation of the left ascending coronary artery (MI) or sham surgery. The MI and sham animals were randomly allocated to treatment with placebo or apixaban in the chow (150 mg/kg/day), starting 2 weeks after surgery. Cardiac function was assessed using echocardiography and histological and molecular markers of cardiac hypertrophy were assessed in the left ventricle (LV). Apixaban resulted in a fivefold increase in anti-FXa activity compared with vehicle, but no overt bleeding was observed and haematocrit levels remained similar in apixaban- and vehicle-treated groups. After 10 weeks of treatment, LV ejection fraction was 42 ± 3% in the MI group treated with apixaban and 37 ± 2 in the vehicle-treated MI group (p > 0.05). Both vehicle- and apixaban-treated MI groups also displayed similar degrees of LV dilatation, LV hypertrophy and interstitial fibrosis. Histological and molecular markers for pathological remodelling were also comparable between groups, as was the activity of signalling pathways downstream of the PAR1 receptor. CONCLUSION: FXa inhibition with apixaban does not influence pathological cardiac remodelling after MI. These data do not support the use of FXa inhibitor in HF patients with the aim to amend the severity of HF. Graphical Abstract.

Ketone Ester Treatment Improves Cardiac Function and Reduces Pathologic Remodeling in Preclinical Models of Heart Failure.

BACKGROUND: Accumulating evidence suggests that the failing heart reprograms fuel metabolism toward increased utilization of ketone bodies and that increasing cardiac ketone delivery ameliorates cardiac dysfunction. As an initial step toward development of ketone therapies, we investigated the effect of chronic oral ketone ester (KE) supplementation as a prevention or treatment strategy in rodent heart failure models. METHODS: Two independent rodent heart failure models were used for the studies: transverse aortic constriction/myocardial infarction (MI) in mice and post-MI remodeling in rats. Seventy-five mice underwent a prevention treatment strategy with a KE comprised of hexanoyl-hexyl-3-hydroxybutyrate KE (KE-1) diet, and 77 rats were treated in either a prevention or treatment regimen using a commercially available ß-hydroxybutyrate-(R)-1,3-butanediol monoester (DeltaG; KE-2) diet. RESULTS: The KE-1 diet in mice elevated ß-hydroxybutyrate levels during nocturnal feeding, whereas the KE-2 diet in rats induced ketonemia throughout a 24-hour period. The KE-1 diet preventive strategy attenuated development of left ventricular dysfunction and remodeling post-transverse aortic constriction/MI (left ventricular ejection fraction±SD, 36±8 in vehicle versus 45±11 in KE-1; P=0.016). The KE-2 diet therapeutic approach also attenuated left ventricular dysfunction and remodeling post-MI (left ventricular ejection fraction, 41±11 in MI-vehicle versus 61±7 in MI-KE-2; P<0.001). In addition, ventricular weight, cardiomyocyte cross-sectional area, and the expression of ANP (atrial natriuretic peptide) were significantly attenuated in the KE-2-treated MI group. However, treatment with KE-2 did not influence cardiac fibrosis post-MI. The myocardial expression of the ketone transporter and 2 ketolytic enzymes was significantly increased in rats fed KE-2 diet along with normalization of myocardial ATP levels to sham values. CONCLUSIONS: Chronic oral supplementation with KE was effective in both prevention and treatment of heart failure in 2 preclinical animal models. In addition, our results indicate that treatment with KE reprogrammed the expression of genes involved in ketone body utilization and normalized myocardial ATP production following MI, consistent with provision of an auxiliary fuel. These findings provide rationale for the assessment of KEs as a treatment for patients with heart failure.

Effects of Sodium-Glucose Co-transporter 2 Inhibition with Empaglifozin on Renal Structure and Function in Non-diabetic Rats with Left Ventricular Dysfunction After Myocardial Infarction.

BACKGROUND: The use of sodium-glucose co-transporter 2 inhibitors (SGLT2i) is currently expanding to cardiovascular risk reduction in non-diabetic subjects, but renal (side-)effects are less well studied in this setting. METHODS: Male non-diabetic Sprague Dawley rats underwent permanent coronary artery ligation to induce MI, or sham surgery. Rats received chow containing empagliflozin (EMPA) (30 mg/kg/day) or control chow. Renal function and electrolyte balance were measured in metabolic cages. Histological and molecular markers of kidney injury, parameters of phosphate homeostasis and bone resorption were also assessed. RESULTS: EMPA resulted in a twofold increase in diuresis, without evidence for plasma volume contraction or impediments in renal function in both sham and MI animals. EMPA increased plasma magnesium levels, while the levels of glucose and other major electrolytes were comparable among the groups. Urinary protein excretion was similar in all treatment groups and no histomorphological alterations were identified in the kidney. Accordingly, molecular markers for cellular injury, fibrosis, inflammation and oxidative stress in renal tissue were comparable between groups. EMPA resulted in a slight increase in circulating phosphate and PTH levels without activating FGF23-Klotho axis in the kidney and bone mineral resorption, measured with CTX-1, was not increased. CONCLUSIONS: EMPA exerts profound diuretic effects without compromising renal structure and function or causing significant electrolyte imbalance in a non-diabetic setting. The slight increase in circulating phosphate and PTH after EMPA treatment was not associated with evidence for increased bone mineral resorption suggesting that EMPA does not affect bone health.

Sodium-glucose co-transporter 2 inhibition as a mitochondrial therapy for atrial fibrillation in patients with diabetes?

While patients with type 2 diabetes mellitus (T2DM) are at increased risk to develop atrial fibrillation (AF), the mechanistic link between T2DM and AF-susceptibility remains unclear. Common co-morbidities of T2DM, particularly hypertension, may drive AF in the setting of T2DM. But direct mechanisms may also explain this relation, at least in part. In this regard, recent evidence suggests that mitochondrial dysfunction drives structural, electrical and contractile remodelling of atrial tissue in patients T2DM. Mitochondrial dysfunction may therefore be the mechanistic link between T2DM and AF and could also serve as a therapeutic target. An elegant series of experiments published in Cardiovascular Diabetology provide compelling new evidence to support this hypothesis. Using a model of high fat diet (HFD) and low-dose streptozotocin (STZ) injection, Shao et al. provide data that demonstrate a direct association between mitochondrial dysfunction and the susceptibility to develop AF. But the authors also demonstrated that the sodium-glucose co-transporter 2 inhibitors (SGLT2i) empagliflozin has the capacity to restore mitochondrial function, ameliorate electrical and structural remodelling and prevent AF. These findings provide a new horizon in which mitochondrial targeted therapies could serve as a new class of antiarrhythmic drugs.

Sodium-glucose co-transporter 2 inhibition with empagliflozin improves cardiac function in non-diabetic rats with left ventricular dysfunction after myocardial infarction.

AIMS: Sodium-glucose co-transporter 2 (SGLT2) inhibition reduces heart failure hospitalizations in patients with diabetes, irrespective of glycaemic control. We examined the effect of SGLT2 inhibition with empagliflozin (EMPA) on cardiac function in non-diabetic rats with left ventricular (LV) dysfunction after myocardial infarction (MI). METHODS AND RESULTS: Non-diabetic male Sprague-Dawley rats underwent permanent coronary artery ligation to induce MI, or sham surgery. Rats received chow containing EMPA that resulted in an average daily intake of 30 mg/kg/day or control chow, starting before surgery (EMPA-early) or 2 weeks after surgery (EMPA-late). Cardiac function was assessed using echocardiography and histological and molecular markers of cardiac remodelling and metabolism were assessed in the left ventricle. Renal function was assessed in metabolic cages. EMPA increased urine production by two-fold without affecting creatinine clearance and serum electrolytes. EMPA did not influence MI size, but LV ejection fraction (LVEF) was significantly higher in the EMPA-early and EMPA-late treated MI groups compared to the MI group treated with vehicle (LVEF 54%, 52% and 43%, respectively, all P < 0.05). EMPA also attenuated cardiomyocyte hypertrophy, diminished interstitial fibrosis and reduced myocardial oxidative stress. EMPA treatment reduced mitochondrial DNA damage and stimulated mitochondrial biogenesis, which was associated with the normalization of myocardial uptake and oxidation of glucose and fatty acids. EMPA increased circulating ketone levels as well as myocardial expression of the ketone body transporter and two critical ketogenic enzymes, indicating that myocardial utilization of ketone bodies was increased. Together these metabolic changes were associated with an increase in cardiac ATP production. CONCLUSION: Empagliflozin favourably affects cardiac function and remodelling in non-diabetic rats with LV dysfunction after MI, associated with substantial improvements in cardiac metabolism and cardiac ATP production. Importantly, it did so without renal adverse effects. Our data suggest that EMPA might be of benefit in heart failure patients without diabetes.

Unraveling the Molecular Mechanism of Action of Empagliflozin in Heart Failure With Reduced Ejection Fraction With or Without Diabetes.

The mechanism of action of empagliflozin in heart failure with reduced ejection fraction (HFrEF) was deciphered using deep learning in silico analyses together with in vivo validation. The most robust mechanism of action involved the sodium-hydrogen exchanger (NHE)-1 co-transporter with 94.7% accuracy, which was similar for diabetics and nondiabetics. Notably, direct NHE1 blockade by empagliflozin ameliorated cardiomyocyte cell death by restoring expression of X-linked inhibitor of apoptosis (XIAP) and baculoviral IAP repeat-containing protein 5 (BIRC5). These results were independent of diabetes mellitus comorbidity, suggesting that empagliflozin may emerge as a new treatment in HFrEF.