Animal models of heart failure with preserved ejection fraction (HFpEF): from metabolic pathobiology to drug discovery

The treatment with soluble guanylate cyclase stimulator BAY41-8543 prevents malignant hypertension and associated organ damage

OBJECTIVE

Despite availability of an array of antihypertensive drugs, malignant hypertension remains a life-threatening condition, and new therapeutic strategies for the treatment of malignant hypertension and malignant hypertension-associated organ damage are needed. The aim of the present study was to assess the effects of nitric oxide (NO)-independent soluble guanylyl cyclase (sGC) stimulator on the course of malignant hypertension. The second aim was to investigate if the treatment with sodium-glucose cotransporter type 2 (SGLT2) inhibitor would augment the expected beneficial actions of the sGC stimulation on the course of malignant hypertension.

METHODS

As a model of malignant hypertension, Ren-2 transgenic rats (TGR) treated with nonspecific NO synthase inhibitor (Nω-nitro- l-arginine methyl ester, l-NAME) was used. Blood pressure (BP) was monitored by radiotelemetry, and the treatment was started 3 days before administration of l-NAME.

RESULTS

The treatment with sGC stimulator BAY 41-8543, alone or combined with SGLT2 inhibitor empagliflozin, abolished malignant hypertension-related mortality in TGR receiving l-NAME. These two treatment regimens also prevented BP increases after l-NAME administration in TGR, and even decreased BP below values observed in control TGR, and prevented cardiac dysfunction and malignant hypertension-related morbidity. The treatment with the SGLT2 inhibitor empagliflozin did not further augment the beneficial actions of sGC stimulator on the course of malignant hypertension-related mortality.

CONCLUSION

The treatment with NO-independent sGC stimulator displayed marked protective actions on the course of malignant hypertension-related mortality and malignant hypertension-related cardiac damage. This suggests that application of sGC stimulator could be a promising therapeutic means for the treatment of malignant hypertension.

Cardiometabolic Phenotype in HFpEF: Insights from Murine Models

Heart failure with preserved ejection fraction (HFpEF) remains a significant challenge in modern healthcare. It accounts for the majority of heart failure cases and their number worldwide is steadily increasing. With its high prevalence and substantial clinical impact, therapeutic strategies for HFpEF are still inadequate. This review focuses on the cardiometabolic phenotype of HFpEF which is characterised by such conditions as obesity, type 2 diabetes mellitus, and hypertension. Various murine models that mimic this phenotype are discussed. Each model's pathophysiological aspects, namely inflammation, oxidative stress, endothelial dysfunction, changes in cardiomyocyte protein function, and myocardial metabolism alterations are examined in detail. Understanding these models can provide insight into the mechanisms underlying HFpEF and aid in the development of effective therapeutic interventions.

Modeling Heart Failure With Preserved Ejection Fraction Using Human Induced Pluripotent Stem Cell-Derived Cardiac Organoids

BACKGROUND

The therapeutic armamentarium for heart failure with preserved ejection fraction (HFpEF) remains notably constrained. A factor contributing to this problem could be the scarcity of in vitro models for HFpEF, which hinders progress in developing new therapeutic strategies. Here, we aimed at developing a novel, comorbidity-inspired, human, in vitro model for HFpEF.

METHODS

Human induced pluripotent stem cells-derived cardiomyocytes were used to produce cardiac organoids. The generated organoids were then subjected to HFpEF-associated, comorbidity-inspired conditions, such as hypertension, diabetes, and obesity-related inflammation. To assess the development of HFpEF pathophysiological features, organoids were thoroughly evaluated for their structural, functional, electrophysiological, and metabolic properties.

RESULTS

Exposure to the combination of all comorbidity-mimicking conditions resulted in the largest cellular volume of 1692±52 versus 1346±84 µm3 in RPMI (Roswell Park Memorial Institute medium) control group (P=0.003), while lower in obesity, hypertension, and diabetes groups: 1059±40 µm3 (P=0.014), 1276±35 µm3 (P=0.940), and 1575±70 µm3 (P=0.146), respectively. Similarly, ultrastructural fibrosis was most significantly observed after exposure to the combination of all HFpEF-inducing conditions 14.6±1.2% compared with single condition exposure 5.2±1.3% (obesity), 6.7±3.5% (hypertension), and 9.0±1.1% (diabetes; P<0.001). Moreover, HFpEF-related conditions led to an increase in passive force compared with control (7.52±1.08 versus 2.33±0.46 mN/mm, P<0.001), whereas no significant alterations were noted in active contractile forces. Relaxation constant τ was significantly prolonged after exposure to HFpEF conditions showing a prolongation of 95.9 ms (36.4-106.4; P=0.028) compared with a shortening of 35.6 ms (43.3-67.3; P=0.80) in the control. Finally, organoid exposure to HFpEF conditions led to a significant increase in oxidative stress levels and a significant decline in oxygen consumption rate.

CONCLUSIONS

We established a novel, human, in vitro model for HFpEF, based on comorbidity-inspired conditions. The model faithfully recapitulated the structural, functional, and mechanistic features of HFpEF. This model holds the potential to provide mechanistic insights and facilitate the identification of novel therapeutic targets.

Housing temperature influences metabolic phenotype of heart failure with preserved ejection fraction in J vs N strain C57BL/6 mice

Preclinical heart failure studies rely heavily on mouse models despite their higher metabolic and heart rates compared to humans. This study examines how mouse strain (C57BL/6J vs. C57BL/6N) and housing temperature (23 °C vs. 30 °C) affect a well-established two-hit HFpEF model using high-fat diet with L-NAME treatment in male C57BL/6 mouse. Metabolic parameters and cardiac function were assessed at baseline, week 5, and week 15. Thermoneutral housing (30 °C) reduced early diastolic dysfunction in the J strain and altered metabolic profiles in both strains, decreasing energy expenditure and fat oxidation. The J strain specifically showed reduced respiratory exchange ratio and glucose oxidation at 30 °C. While physical activity remained constant across groups, both strains exhibited increased cardiac fibrosis and inflammatory gene expression under HFD + L-NAME, independent of housing temperature. These findings reveal strain-specific physiological adaptations to housing temperature, emphasizing the need to consider environmental conditions in heart failure research carefully.

The Impact of Obesity on Cardiac Energy Metabolism and Efficiency in Heart Failure With Preserved Ejection Fraction

The incidence and prevalence of heart failure with preserved ejection fraction (HFpEF) continues to rise, and now comprises more than half of all heart failure cases. There are many risk factors for HFpEF, including older age, hypertension, diabetes, dyslipidemia, sedentary behaviour, and obesity. The rising prevalence of obesity in society is a particularly important contributor to HFpEF development and severity. Obesity can adversely affect the heart, including inducing marked alterations in cardiac energy metabolism. This includes obesity-induced impairments in mitochondrial function, and an increase in fatty acid uptake and mitochondrial fatty acid β-oxidation. This increase in myocardial fatty acid metabolism is accompanied by an impaired myocardial insulin signaling and a marked decrease in glucose oxidation. This switch from glucose to fatty acid metabolism decreases cardiac efficiency and can contribute to severity of HFpEF. Increased myocardial fatty acid uptake in obesity is also associated with the accumulation of fatty acids, resulting in cardiac lipotoxicity. Obesity also results in dramatic changes in the release of adipokines, which can negatively impact cardiac function and energy metabolism. Obesity-induced increases in epicardial fat can also increase cardiac insulin resistance and negatively affect cardiac energy metabolism and HFpEF. However, optimizing cardiac energy metabolism in obese subjects may be one approach to preventing and treating HFpEF. This review discusses what is presently known about the effects of obesity on cardiac energy metabolism and insulin signaling in HFpEF. The clinical implications of obesity and energy metabolism on HFpEF are also discussed.

Advances in myocardial energy metabolism: metabolic remodelling in heart failure and beyond

The very high energy demand of the heart is primarily met by adenosine triphosphate (ATP) production from mitochondrial oxidative phosphorylation, with glycolysis providing a smaller amount of ATP production. This ATP production is markedly altered in heart failure, primarily due to a decrease in mitochondrial oxidative metabolism. Although an increase in glycolytic ATP production partly compensates for the decrease in mitochondrial ATP production, the failing heart faces an energy deficit that contributes to the severity of contractile dysfunction. The relative contribution of the different fuels for mitochondrial ATP production dramatically changes in the failing heart, which depends to a large extent on the type of heart failure. A common metabolic defect in all forms of heart failure [including heart failure with reduced ejection fraction (HFrEF), heart failure with preserved EF (HFpEF), and diabetic cardiomyopathies] is a decrease in mitochondrial oxidation of pyruvate originating from glucose (i.e. glucose oxidation). This decrease in glucose oxidation occurs regardless of whether glycolysis is increased, resulting in an uncoupling of glycolysis from glucose oxidation that can decrease cardiac efficiency. The mitochondrial oxidation of fatty acids by the heart increases or decreases, depending on the type of heart failure. For instance, in HFpEF and diabetic cardiomyopathies myocardial fatty acid oxidation increases, while in HFrEF myocardial fatty acid oxidation either decreases or remains unchanged. The oxidation of ketones (which provides the failing heart with an important energy source) also differs depending on the type of heart failure, being increased in HFrEF, and decreased in HFpEF and diabetic cardiomyopathies. The alterations in mitochondrial oxidative metabolism and glycolysis in the failing heart are due to transcriptional changes in key enzymes involved in the metabolic pathways, as well as alterations in redox state, metabolic signalling and post-translational epigenetic changes in energy metabolic enzymes. Of importance, targeting the mitochondrial energy metabolic pathways has emerged as a novel therapeutic approach to improving cardiac function and cardiac efficiency in the failing heart.

The aging heart in focus: The advanced understanding of heart failure with preserved ejection fraction

Heart failure with preserved ejection fraction (HFpEF) accounts for 50 % of heart failure (HF) cases, making it the most common type of HF, and its prevalence continues to increase in the aging society. HFpEF is a systemic syndrome resulting from many risk factors, such as aging, metabolic syndrome, and hypertension, and its clinical features are highly heterogeneous in different populations. HFpEF syndrome involves the dysfunction of multiple organs, including the heart, lung, muscle, and vascular system. The heart shows dysfunction of various cells, including cardiomyocytes, endothelial cells, fibroblasts, adipocytes, and immune cells. The complex etiology and pathobiology limit experimental research on HFpEF in animal models, delaying a comprehensive understanding of the mechanisms and making treatment difficult. Recently, many scientists and cardiologists have attempted to improve the clinical outcomes of HFpEF. Recent advances in clinically related animal models and systemic pathology studies have improved our understanding of HFpEF, and clinical trials involving sodium-glucose cotransporter 2 inhibitors have significantly enhanced our confidence in treating HFpEF. This review provides an updated comprehensive discussion of the etiology and pathobiology, molecular and cellular mechanisms, preclinical animal models, and therapeutic trials in animals and patients to enhance our understanding of HFpEF and improve clinical outcomes.

Epidemiology and Management of Patients With Kidney Disease and Heart Failure With Preserved Ejection Fraction

Heart failure with preserved ejection fraction (HFpEF) comprises approximately one-half of all diagnoses of heart failure. There is significant overlap of this clinical syndrome with chronic kidney disease (CKD), with many shared comorbid conditions. The presence of CKD in patients with HFpEF is one of the most powerful risk factors for adverse clinical outcomes, including death and heart failure hospitalization. The pathophysiology linking HFpEF and CKD remains unclear, but it is postulated to consist of numerous bidirectional pathways, including endothelial dysfunction, inflammation, obesity, insulin resistance, and impaired sodium handling. The diagnosis of HFpEF requires certain criteria to be satisfied, including signs and symptoms consistent with volume overload caused by structural or functional cardiac abnormalities and evidence of increased cardiac filling pressures. There are numerous overlapping metabolic clinical syndromes in patients with HFpEF and CKD that can serve as targets for intervention. With an increasing number of therapies available for HFpEF and CKD as well as for obesity and diabetes, improved recognition and diagnosis are paramount for appropriate management and improved clinical outcomes in patients with both HFpEF and CKD.

Myocardial Metabolism in Heart Failure with Preserved Ejection Fraction

Heart failure with preserved ejection fraction (HFpEF) is increasingly prevalent and now accounts for half of all heart failure cases. This rise is largely attributed to growing rates of obesity, hypertension, and diabetes. Despite its prevalence, the pathophysiological mechanisms of HFpEF are not fully understood. The heart, being the most energy-demanding organ, appears to have a compromised bioenergetic capacity in heart failure, affecting all phenotypes and aetiologies. While metabolic disturbances in heart failure with reduced ejection fraction (HFrEF) have been extensively studied, similar insights into HFpEF are limited. This review collates evidence from both animal and human studies, highlighting metabolic dysregulations associated with HFpEF and its risk factors, such as obesity, hypertension, and diabetes. We discuss how changes in substrate utilisation, oxidative phosphorylation, and energy transport contribute to HFpEF. By delving into these pathological shifts in myocardial energy production, we aim to reveal novel therapeutic opportunities. Potential strategies include modulating energy substrates, improving metabolic efficiency, and enhancing critical metabolic pathways. Understanding these aspects could be key to developing more effective treatments for HFpEF.