Sex Differences in Heart Mitochondria: Relationship to Diastolic Dysfunction

As part of genetic studies of heart failure in mice, we observed that heart mitochondrial DNA levels and function tend to be reduced in females as compared to males. We also observed that expression of genes encoding mitochondrial proteins were higher in males than females in human cohorts. Heart failure with preserved ejection fraction (HFpEF) exhibits a sex bias, being more common in women than men, and we hypothesized that mitochondrial sex differences might underlie this bias. We tested this in a panel of genetically diverse inbred strains of mice, termed the Hybrid Mouse Diversity Panel (HMDP). Indeed, we found that mitochondrial gene expression was highly correlated with diastolic function, a key trait in HFpEF. Consistent with this, studies of a “two-hit” mouse model of HFpEF confirmed that mitochondrial function differed between sexes and was strongly associated with a number of HFpEF traits. By integrating data from human heart failure and the mouse HMDP cohort, we identified the mitochondrial protein Acsl6 as a genetic determinant of diastolic function. We validated its role in HFpEF using adenoviral over-expression in the heart. We conclude that sex differences in mitochondrial function underlie, in part, the sex bias in diastolic function. C57BL/6J mice were placed on either a control diet (chow) or a high-fat diet supplemented with L-NAME. Heart tissue was isolated from the resulting 8 pairs of male mice and 7 pairs of female mice and RNA extracted from these hearts were sequenced. Differential expression was performed on the resulting counts.本研究隶属于小鼠心力衰竭遗传学研究范畴，我们观察到：相较于雄性小鼠，雌性小鼠的心脏线粒体DNA水平与线粒体功能普遍降低。同时，我们在人类队列中也观察到，雄性个体中编码线粒体蛋白的基因表达水平高于雌性。射血分数保留型心力衰竭（Heart failure with preserved ejection fraction, HFpEF）存在性别偏倚，女性患病率高于男性，据此我们提出假设：线粒体相关的性别差异可能是该性别偏倚的潜在成因。我们借助遗传多样性近交系小鼠集合——杂交小鼠多样性面板（Hybrid Mouse Diversity Panel, HMDP）验证了这一假设。实验结果证实，线粒体基因表达水平与舒张功能（HFpEF的关键临床特征之一）呈高度相关。与此一致，针对HFpEF的“双打击”小鼠模型的研究证实，不同性别间的线粒体功能存在差异，且与多项HFpEF相关表型显著相关。通过整合人类心力衰竭数据与小鼠HMDP队列数据，我们鉴定出线粒体蛋白Acsl6为舒张功能的遗传调控因子。我们通过心脏腺病毒过表达实验，验证了Acsl6在HFpEF发病过程中的作用。综上，我们得出结论：线粒体功能的性别差异是舒张功能性别偏倚的部分成因。将C57BL/6J小鼠分为两组，分别喂食正常对照饲料（标准啮齿类饲料）与添加L-NAME的高脂饲料。随后从实验得到的8只雄性小鼠与7只雌性小鼠中分离心脏组织，提取心脏总RNA并进行测序；基于得到的计数数据开展差异表达分析。