Aim Sex-differences in heart failure with preserved ejection fraction (HFpEF) are important, but key mechanisms involved are incompletely understood. While animal models can inform about sex-dependent cellular and molecular changes, many previous preclinical HFpEF models have failed to recapitulate sex-dependent characteristics of human HFpEF. We tested for sex-differences in HFpEF using a two-hit mouse model (leptin receptor-deficient db/db mice plus aldosterone infusion for 4 weeks; db/db+Aldo). Methods and Results We performed echocardiography, electrophysiology, intracellular Ca2+ imaging, and protein analysis. Female HFpEF mice exhibited more severe diastolic dysfunction in line with increased titin N2B isoform expression and PEVK element phosphorylation, and reduced troponin-I phosphorylation. Female HFpEF mice had lower BNP levels than males despite similar comorbidity burden (obesity, diabetes) and cardiac hypertrophy in both sexes. Male HFpEF mice were more susceptible to cardiac alternans. Male HFpEF cardiomyocytes (versus female) exhibited higher diastolic [Ca2+], slower Ca2+ transient decay, reduced L-type Ca2+ current, more pronounced enhancement of the late Na+ current, and increased short-term variability of action potential duration (APD). However, male and female HFpEF myocytes showed similar downregulation of inward rectifier and transient outward K+ currents, APD prolongation, and frequency of delayed afterdepolarizations. Inhibition of Ca2+/calmodulin-dependent protein kinase II (CaMKII) reversed all pathological APD changes in HFpEF in both sexes, and empagliflozin pretreatment mimicked these effects of CaMKII inhibition. Vericiguat had only slight benefits, and these effects were larger in HFpEF females. Conclusion We conclude that the db/db+Aldo preclinical HFpEF murine model recapitulates key sex-specific mechanisms in HFpEF and provides mechanistic insights into impaired excitation-contraction coupling and sex-dependent differential arrhythmia susceptibility in HFpEF with potential therapeutic implications. In male HFpEF myocytes, altered Ca2+ handling and electrophysiology aligned with diastolic dysfunction and arrhythmias, while worse diastolic dysfunction in females may depend more on altered myofilaments properties.

中文翻译：

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肥胖糖尿病 HFpEF 模型心肌细胞对舒张功能障碍和心律失常的性别依赖性差异易感性

射血分数保留性心力衰竭（HFpEF）的性别差异很重要，但所涉及的关键机制尚不完全清楚。虽然动物模型可以了解性别依赖性细胞和分子变化，但许多先前的临床前 HFpEF 模型未能重现人类 HFpEF 的性别依赖性特征。我们使用两次打击小鼠模型（瘦素受体缺陷的 db/db 小鼠加醛固酮输注 4 周；db/db+Aldo）测试了 HFpEF 的性别差异。方法和结果 我们进行了超声心动图、电生理学、细胞内 Ca2+ 成像和蛋白质分析。雌性 HFpEF 小鼠表现出更严重的舒张功能障碍，这与肌联蛋白 N2B 亚型表达和 PEVK 元件磷酸化增加以及肌钙蛋白-I 磷酸化减少一致。尽管雌性 HFpEF 小鼠的合并症负担（肥胖、糖尿病）和心脏肥大相似，但雌性 HFpEF 小鼠的 BNP 水平低于雄性。雄性 HFpEF 小鼠更容易受到心脏交替的影响。男性 HFpEF 心肌细胞（与女性相比）表现出更高的舒张压 [Ca2+]、更慢的 Ca2+ 瞬时衰减、降低的 L 型 Ca2+ 电流、更明显的晚期 Na+ 电流增强以及增加的动作电位持续时间 (APD) 的短期变异性。然而，男性和女性 HFpEF 肌细胞表现出相似的内向整流和瞬时外向 K+ 电流、APD 延长和延迟后除极频率的下调。 Ca2+/钙调蛋白依赖性蛋白激酶 II (CaMKII) 的抑制可逆转两性 HFpEF 的所有病理性 APD 变化，恩格列净预处理模仿了 CaMKII 抑制的这些作用。 Vericiguat 仅具有轻微的益处，并且这些作用对于 HFpEF 女性来说更大。结论 我们得出的结论是，db/db+Aldo 临床前 HFpEF 小鼠模型概括了 HFpEF 的关键性别特异性机制，并为 HFpEF 中兴奋-收缩耦合受损和性别依赖性心律失常易感性受损提供了机制见解，具有潜在的治疗意义。在男性 HFpEF 肌细胞中，Ca2+ 处理和电生理学的改变与舒张功能障碍和心律失常相关，而女性中更严重的舒张功能障碍可能更多地取决于肌丝特性的改变。