Cracking the Code of a Preclinical Rodent Model of HFpEF

Corresponding Author

Heart failure with preserved ejection fraction (HFpEF) represents a growing public health burden, now accounting for over 50% of all heart failure cases.¹ However, there are several therapeutic challenges present because of the heterogeneous pathophysiology of HFpEF and its limited treatment options. Recognizing these barriers, the National Institution of Health—National Heart, Lung, and Blood Institute convened a working group to establish research priorities for HFpEF, which emphasized the development of preclinical models that well recapitulate the human disease phenotype.² According to the working group recommendations, ideal preclinical models should recapitulate multiple features of HFpEF, including diastolic dysfunction, preserved ejection fraction, systemic inflammation, multiorgan involvement, metabolic syndrome, exercise intolerance, and age-related comorbid conditions.²

A range of large animal models, including swine, canine, and feline models, have been used to study pressure overload and diastolic dysfunction, offering the advantage of similar cardiac physiology to humans.³ However, their high cost and limited accessibility make their use impractical for mechanistic studies and therapeutic screening. In contrast, rodent models offer scalable platforms for preclinical exploration; yet, most models capture only partial aspects of HFpEF. For instance, models based on angiotensin II or phenylephrine infusion simulate hypertension and concentric hypertrophy but lack systemic metabolic dysfunction. Western diet–induced obesity models reproduce insulin resistance but often fail to induce overt cardiac dysfunction. Senescence-accelerated aging mice mimic age-related changes but exhibit inconsistent hemodynamic phenotypes.³ Among these, the ZSF1 obese rat has emerged as a particularly robust “multi-hit” model, reflecting many key features of human HFpEF, including obesity, insulin resistance, hypertension, and diastolic dysfunction.⁴ Thus, ZSF1 provides a valuable platform for evaluating mechanistic pathways and pharmacologic interventions in HFpEF. ZSF1 rat is a hybrid rodent model that was generated by crossing a Zucker diabetic fatty female rat carrying a leptin receptor missense sequence variant (Lepr^+/fa) with a spontaneously hypertensive heart failure (SHHF) male rat with another leptin receptor mutation (Lepr^cp) heterozygote. The resulting offspring produce 2 different strains with distinct phenotypes: a healthy lean phenotype (hypertension) and obese phenotype (Lepr^fa/cp) that is prone to diabetes, hypertension, and HFpEF.⁵

In this issue of JACC: Basic to Translational Science, Gibb et al⁶ provide critical mechanistic insights and establish a foundation for the development of targeted therapies in HFpEF through multi-omics profiling of the ZSF1 obese rat model. In this study, the authors compared the ZSF1-obese rat, a widely used model of HFpEF, not only with its lean counterpart but also with Wistar-Kyoto (WKY) rats as healthy controls. This design allowed a stepwise examination of disease progression. ZSF1-lean rats, which develop hypertension without clear features of HFpEF, showed subtle transcriptomic changes compared with WKY controls (233 genes). In contrast, ZSF1-obese rats exhibited additional transcriptomic pathway alterations that reflect the full HFpEF phenotype compared with the ZSF1 group (5,691 genes). Importantly, the study focused on the early stage of HFpEF development by utilizing 14-week-old ZSF1 rats, whereas most previous studies employed animals at 20 to 24 weeks of age when disease features are already well established. This early time point allowed the authors to capture pathophysiological mechanisms at disease development stage, offering insights into potential preventive and therapeutic targets.

Through integrated transcriptomic and metabolomic profiling, the study identified significant alterations in central metabolic pathways, including the glycolysis, tricarboxylic acid (TCA) cycle, and fatty acid beta-oxidation, in the ZSF1-obese hearts. Notably, these metabolic shifts converged on mitochondrial ATP production, a finding that was phenotypically validated through detailed mitochondrial analyses. Using transmission electron microscopy, the authors demonstrated marked abnormalities in mitochondrial morphology and lipid droplet distribution, indicating structural correlates of metabolic dysfunction. Moreover, mitochondrial calcium uptake capacity, which is a key determinant of cellular bioenergetics, was found to be impaired, reinforcing the central role of mitochondrial dysfunction in early HFpEF pathogenesis.

HFpEF was first recognized in clinical practice, and as a result, clinical investigations have progressed more rapidly than preclinical studies. Recently, a growing number of clinical omics studies7, 8, 9 have revealed detailed molecular and metabolic profiles of HFpEF. Thus, alignment between findings in preclinical models and human studies greatly enhances the translational value of animal research for both drug discovery and mechanistic exploration. Notably, the transcriptomic and metabolomic alterations observed in the ZSF1-obese model closely resemble those reported in clinical studies (Figure 1).^7,8 Key examples include the general down-regulation of glycolysis, TCA cycle, branched-chain amino acid, and ketone metabolism-related genes. These changes in RNA levels of these key metabolic genes are strongly linked to the mitochondrial structural and functional abnormalities demonstrated in this study. Clinical research, by its nature, has limited access to the early stages of HFpEF progression. In contrast, well-characterized preclinical models such as the 14-week-old ZSF1-obese rat offer a unique opportunity to identify early-stage biomarkers and explore preventive interventions. Thus, such models are indispensable for advancing both our mechanistic understanding and therapeutic strategies in HFpEF.

Figure 1.

Integrative View of Metabolism Pathways in HFpEF

Comparison of major cardiac metabolism pathways between ZSF1-Obese preclinical model of heart failure with preserved ejection fraction (HFpEF)⁶ and clinical multi-omics analysis.7, 8, 9 In HFpEF, most metabolic pathways are down-regulated. Notably, while human transcriptomic data showed increased oxidative phosphorylation (OXPHOS)-related genes, proteomic and metabolomic data revealed a decrease in OXPHOS activity, indicating a mismatch between gene and protein expression. Image adapted with permission from the National Institutes of Health BioArt source.¹⁰

One of the notable strengths of this study is the inclusion of both ZSF1-lean and healthy WKY controls, which allowed for a detailed assessment of disease progression. Surprisingly, the transcriptomic changes in metabolic genes observed in the ZSF1-obese group were largely absent in the ZSF1-lean rats. However, metabolomic profiling revealed 278 significantly altered metabolites, highlighting a disconnect between gene expression and metabolite levels. This gap underscores the need for proteomic analyses to bridge transcriptomic and metabolomic data and clarify pathway changes. Furthermore, given that metabolic shifts can influence epigenetic regulation, future investigations should evaluate changes in DNA methylation, histone modifications, and post-translational modifications (eg, acylation, and O-GlcNAcylation). These studies may offer mechanistic insights into how metabolic dysfunction promotes HFpEF progression and may inform the development of epigenetic-targeted therapies.

Although no overt sex-based phenotypic differences were reported in this study, HFpEF disproportionately affects postmenopausal women in clinical settings.² Future work should include aged female models to better capture sex-specific disease drivers and improve translational relevance. Recent clinical metabolomic and proteomic studies have increasingly employed subgroup analyses.^7,8 Similarly, preclinical studies should adopt stratified designs that consider sex, age, body weight, and metabolic markers such as blood glucose. This approach may reveal heterogeneity in therapeutic responses and improve translational relevance.

Additionally, in-depth comparisons between clinical omics data and the current findings may help further define the limitations of the ZSF1-obese model and guide refinement of preclinical strategies. A key unresolved question is whether mitochondrial dysfunction is a primary event or a secondary consequence of metabolic remodeling. Clarifying this “chicken-or-egg” relationship will be essential to determine optimal therapeutic targets and timing.

Last, HFpEF is a systemic syndrome involving complex interplay among the heart, skeletal muscle, liver, kidneys, and vasculature. A more integrative approach using the ZSF1-obese model will be important for capturing the full spectrum of disease mechanisms. Together, these findings not only enhance our understanding of HFpEF pathogenesis but also open new avenues for early intervention and targeted therapy in this complex HFpEF mechanism. Taken together with the current literature, this study highlights the need for continued discovery and refinement of not only the animal models used but the combination of endpoints examined. That said, with increasing focus on these types of models and the different stages of disease development and progression hopefully key regulatory points will be defined to develop novel therapeutic strategies to combat the relatively complex HFpEF disease manifestation.

Funding Support and Author Disclosures

The authors have reported that they have no relationships relevant to the contents of this paper to disclose.