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

The ketone body 3-hydroxybutyrate increases cardiac output and cardiac contractility in a porcine model of cardiogenic shock: a randomized, blinded, crossover trial

Cardiogenic shock (CS) is characterized by reduced cardiac output (CO), reduced end-organ perfusion, and high mortality. Medical therapies have failed to improve survival. The ketone body 3-hydroxybutyrate (3-OHB) enhances cardiac function in heart failure and CS. We aimed to elucidate the cardiovascular and cardiometabolic effects of 3-OHB treatment during CS. In a randomized, assessor-blinded crossover design, we studied 16 female pigs (60 kg, 5 months of age). CS was induced by left main coronary artery microsphere injections. Predefined criteria for CS were a 30% reduction in CO or mixed venous saturation (SvO2). Intravenous 3-OHB infusion and a matching control solution were administered for 120 min in random order. Hemodynamic measurements were obtained by pulmonary artery catheterization and a left ventricular (LV) pressure-volume catheter. Myocardial mitochondrial function was assessed using high resolution respirometry. During CS, infusion with 3-OHB increased CO by 0.9 L/min (95%CI 0.4-1.3 L/min) compared with control infusion. SvO2 (P = 0.026) and heart rate (P < 0.001) increased. Stroke volume (P = 0.6) was not altered. LV contractile function as determined by LV end-systolic elastance improved during 3-OHB infusion compared with control infusion (P = 0.004). Systemic and pulmonary vascular resistance decreased, and diuresis increased. LV mitochondrial function was higher after 3-OHB infusion compared with control. We conclude that 3-OHB infusion enhances cardiac function by increasing contractility and reducing vascular resistance, while also preserving myocardial mitochondrial respiratory function in a large animal model of ischemic CS. These novel findings support the therapeutic potential of exogenous ketone supplementation in CS management.

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

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

Lactate infusion improves cardiac function in a porcine model of ischemic cardiogenic shock

BACKGROUND

Cardiogenic shock (CS) is associated with high mortality and medical therapies have failed to improve survival. Treatment with lactate is associated with improved cardiac function which may benefit this condition. Comprehensive hemodynamic assessment of lactate administration in CS is lacking, and the mechanisms underlying the cardiovascular effects of lactate in CS have not yet been elucidated. In this study we aimed to study the cardiovascular and cardiometabolic effects of treatment with lactate in experimental ischemic CS.

METHODS

In a randomized, blinded design, 20 female pigs (60 kg) were studied. Left main coronary artery microsphere injections were used to cause CS, defined as a 30% reduction in CO or mixed venous saturation (SvO2). Subjects were randomized to receive either intravenous exogenous lactate or euvolemic, equimolar saline (control) for 180 min. Positive inotropic control with dobutamine was administered on top of ongoing treatment after 180 min. Extensive hemodynamic measurements were obtained from pulmonary artery and left ventricular (LV) pressure-volume catheterization. Furthermore, endomyocardial biopsies were analyzed for mitochondrial function and arterial, renal vein, and coronary sinus blood samples were collected. The primary endpoint was change in CO during 180 min of treatment.

RESULTS

Arterial lactate levels increased from 2.4 ± 1.1 to 7.7 ± 1.1 mmol/L (P < 0.001) during lactate infusion. CO increased by 0.7 L/min (P < 0.001) compared with control, due to increased stroke volume (P = 0.003). Notably, heart rate and mean arterial pressure did not differ significantly between treatments. End-systolic elastance (load independent contractility) was enhanced during lactate infusion (P = 0.048), together with LV ejection fraction (P = 0.009) and dP/dt(max) (P = 0.041). Arterial elastance (afterload) did not differ significantly (P = 0.12). This resulted in improved ventriculo-arterial coupling efficiency (P = 0.012). Cardiac mechanical efficiency (P = 0.003), diuresis (P = 0.016), and SvO2 (P = 0.018) were increased during lactate infusion. Myocardial mitochondrial complex I respiration was enhanced during lactate infusion compared with control (P = 0.04). Concomitant administration of dobutamine on top of lactate resulted in further hemodynamic improvements compared with control.

CONCLUSIONS

Lactate infusion improved cardiac function and myocardial mitochondrial respiration in a porcine model of CS. The hemodynamic effects included increased CO mediated through stroke volume increase. These favorable cardiovascular effects may benefit patients with CS.

Butyrate increases cardiac output and causes vasorelaxation in a healthy porcine model

BACKGROUND

Butyrate, a short-chain fatty acid, has shown potential to improve left ventricular (LV) function and induce vasorelaxation in rodents. Butyrate may either be produced by the microbiome in the colon, be ingested or administered intravenously. This study aimed to evaluate effects of butyrate on cardiac output (CO) and associated hemodynamic variables in a porcine model.

METHODS

In a randomized, blinded crossover study, ten healthy 60-kg pigs were given three hour infusions of 600 mM butyrate and equimolar sodium chloride (control). CO was measured by thermodilution via a pulmonary artery catheter. LV contractility was assessed using pressure-volume admittance catheterization. Additionally, isolated porcine coronary arteries were exposed to butyrate in a wire myograph to evaluate vasorelaxation.

RESULTS

Butyrate infusion increased plasma butyrate concentration to 0.53 mM (95 % confidence interval (CI): 0.49 to 0.58 mM, P < 0.58 mM, P < 0.001) and CO by 1.6 L/min (95 % CI: 1.0 to 2.1 L/min, P < 0.001) compared with the control. Heart rate, LV ejection fraction, cardiac efficiency and dP/dtmax rose, while systemic vascular resistance, arterial elastance, mean arterial pressure and LV end-systolic volume decreased. Load-independent LV contractility and stroke volume did not significantly differ. In the myograph, porcine coronary arteries relaxed in response to butyrate in a concentration-dependent manner.

CONCLUSION

Butyrate increases cardiac output and lowers vascular resistance in a large animal model, through increased HR and systemic vasorelaxation. Load-independent LV contractility was not significantly altered. We observed indices of increased end-organ perfusion. These potentially beneficial cardiovascular properties of butyrate should be further studied.

The Role of Lactate Metabolism in Heart Failure and Cardiogenic Shock: Clinical Insights and Therapeutic Implications

Heart failure (HF) is associated with poor prognosis, especially when it progresses to cardiogenic shock (CS), where survival rates substantially decline. A key area of interest is the role of blood lactate as a biomarker in these conditions. Lactate is produced under normal physiological conditions but increases with impaired tissue perfusion, a hallmark of HF and CS. Elevated lactate levels result from increased production, reduced clearance or both and are often associated with worse outcomes. Traditionally considered a byproduct of anaerobic metabolism, lactate is now recognized as an important energy substrate, particularly in myocardial tissue during periods of metabolic stress. Recent studies suggest that dynamic lactate monitoring, including lactate clearance (LC), may provide critical insights into patients' prognoses and responses to therapy. Serial measurements of lactate have been shown to predict survival in critically ill patients, including those with HF and CS. In CS, elevated lactate levels correlate with increased mortality risk, and LC is emerging as an important parameter in treatment protocols. Despite growing evidence of lactate's clinical relevance, research is needed to establish standardized thresholds and optimal monitoring timelines. Understanding the complexities of lactate metabolism and its role in HF and CS could lead to improved risk stratification and more personalized treatment approaches.

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.

Progress in Lactate Metabolism and Its Regulation via Small Molecule Drugs

Lactate, once viewed as a byproduct of glycolysis and a metabolic "waste", is now recognized as an energy-providing substrate and a signaling molecule that modulates cellular functions under pathological conditions. The discovery of histone lactylation in 2019 marked a paradigm shift, with subsequent studies revealing that lactate can undergo lactylation with both histone and non-histone proteins, implicating it in the pathogenesis of various diseases, including cancer, liver fibrosis, sepsis, ischemic stroke, and acute kidney injury. Aberrant lactate metabolism is associated with disease onset, and its levels can predict disease outcomes. Targeting lactate production, transport, and lactylation may offer therapeutic potential for multiple diseases, yet a systematic summary of the small molecules modulating lactate and its metabolism in various diseases is lacking. This review outlines the sources and clearance of lactate, as well as its roles in cancer, liver fibrosis, sepsis, ischemic stroke, myocardial infarction, and acute kidney injury, and summarizes the effects of small molecules on lactate regulation. It aims to provide a reference and direction for future research.

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).