Excitation-contraction coupling, cardiomyocyte electrophysiology, and transcriptome profiles in two HFpEF murine models: etiology and sex-dependent differences

Heart failure (HF) with preserved ejection fraction (HFpEF) comprises heterogeneous clinical phenotypes and variable comorbidities. Recent two-hit translational animal models, including the hypertensive, nitrosative-stressed mice fed with high-fat diet and l-<i>N</i>^G-nitroarginine methyl ester (HFD + l-NAME) and the obese-diabetic leptin receptor-deficient <i>db/db</i> mice with excess aldosterone (<i>db/db</i> + Aldo), may phenocopy select subgroups of HFpEF. We systematically compared mechanisms of excitation-contraction coupling (ECC), electrophysiology, and gene transcription in these preclinical HFpEF models and between sexes, including morphometry, echocardiography, cellular electrophysiology, intracellular Ca²⁺ imaging, and RNA-sequencing. The multiorgan HFpEF phenotype showed key differences between the two models: <i>db/db</i> + Aldo mice were markedly obese, had severe hyperglycemia and hepatomegaly, whereas male HFD + l-NAME mice had more pronounced cardiac hypertrophy. Diastolic dysfunction (quantified as echocardiographic <i>E/e</i>') was more severe in <i>db/db</i> + Aldo mice and worse in females, whereas females showed milder diastolic dysfunction in HFD + l-NAME. Marked proarrhythmic action potential (AP) changes (prolonged AP duration, increased short-term variability, and reduced alternans threshold) occurred in <i>db/db</i> + Aldo (in both sexes), whereas these AP changes were less severe in male HFD + l-NAME and absent in female HFD + l-NAME. In line with these findings, differential ionic current and Ca²⁺ handling changes occurred between these two HFpEF models and between sexes. RNA-sequencing revealed highly distinctive gene expression profiles between HFpEF models. We conclude that marked differences exist in cardiomyocyte ECC, electrophysiology, and gene expression between HFD + l-NAME and <i>db/db</i> + Aldo mice and between sexes. This indicates that a combination of translational HFpEF models that mimic select HFpEF sub-phenogroups are critical to better understand HFpEF mechanisms for therapeutic drug development.<b>NEW & NOTEWORTHY</b> Excitation-Ca²⁺ signaling-contraction coupling (ECC) mechanisms are fundamental to heart function. ECC mechanisms are differentially altered in murine models of heart failure with preserved ejection fraction (HFpEF) by dominant disease pathology and sex. Diastolic dysfunction is more pronounced in diabetic-obese HFpEF mice (worse in females) than in hypertensive-obese HFpEF mice (female sex is protective). Diabetic-obese mice and primarily hypertensive-obese HFpEF mice exhibit differential ECC alterations and largely distinctive transcription changes, providing mechanistic insights into HFpEF sub-phenogroups.