A new era in modeling metabolic and hemodynamic stressors in HFpEF

Introduction Heart failure with preserved ejection fraction (HFpEF) is a heterogeneous syndrome commonly linked to metabolic and cardiovascular comorbidities, including hypertension, diabetes, obesity, and chronic kidney disease. Left atrial remodeling, characterized by increased volume and dysfunction, is a key feature, contributing to elevated left ventricular filling pressures. Despite growing clinical recognition, the absence of an experimental model that accurately mirrors the complexities of HFpEF poses a major challenge in translational research. Purpose This study aims to refine a recently published HFpEF mouse model by integrating a "two-hit model" combining metabolic (obesity and diabetes) and hemodynamic stress (d-aldosterone infusion). Additionally vascular dysfunction was investigated in this HFpEF model using mouse renal artery. Methods Ten-week-old male and female Leprdb/db mice (n=5-10) and wild-type controls (C57BL6/J, n=5-10) were used. Obesity and diabetes were induced as the first hit, and hemodynamic stress (second hit) was applied using osmotic minipumps delivering d-aldosterone (0.3 µg/h) or vehicle for 4 weeks. Cardiac and vascular functions were assessed by transthoracic echocardiography and wire myography. Results Leprdb/db mice with d-aldosterone infusion exhibited elevated plasma aldosterone levels (609.3 vs. 428.9 pg/mL, p≤ 0.144), preserved ejection fraction (81.46% vs. 66.35%, p≤ 0.0001), reduced cardiac index (0.2104 vs. 0.2974 mL/min/g, p≤ 0.001, and increased heart weight-to-tibia length ratio (7.277 vs. 7.059, p≤ 0.038), indicative of left ventricular hypertrophy. Markers of diastolic dysfunction, including elevated mitral E/A ratio (1.458 vs. 1.237, p≤ 0.016) and E/e' ratio (44.20 vs. 24.01, p≤ 0.001), along with increased left atrial area (3.695 vs. 2.428 mm², p≤ 0.012), were observed. Speckle tracking analysis showed reduced reverse peak strain rates (10.64 vs. 23.92 1/s, p≤ 0.019) and decreased global longitudinal strain (-16.15% vs. -22.68%, p≤ 0.056), indicating diastolic dysfunction and impaired systolic contractility in Leprdb/db mice with d-aldosterone compared to wild-type controls. No evidence of right heart failure or pre-capillary pulmonary hypertension was found, as indicated by preserved lung wet/dry ratio (6.623 vs. 5.012, p≤ 0.05) and normal pulmonary artery pulsatility index, TAPSE, and PAT/PET ratio. Ex vivo wire myography of the aorta and renal arteries revealed impaired endothelium-dependent relaxation in A.renalis (32.76% vs. 57.64, p≤ 0.045) and Aorta (29.85% vs. 63.58%, p≤ 0.0001) as well as enhanced vasoconstriction in A.renalis (120.5 vs. 81.98, p≤ 0.022) and Aorta (182.3% vs. 109.5%, p≤ 0.013) in Leprdb/db mice with d-aldosterone compared to wild-type controls. Conclusion This two-hit HFpEF model effectively replicates key pathological features, including diastolic dysfunction, left atrial remodeling, vascular impairment, fibrosis, and tissue inflammation.Study protocol