Introduction: Heart failure with preserved ejection fraction (HFpEF) affects more women than men and seems to be more associated with oxidative stress and inflammation, suggesting that gender may play a major role in disease evolution. However, studies investigating gender differences in HFpEF are limited. In the present study we aimed to describe gender differences in a well-characterized HFpEF cohort and to elucidate how oxidative stress and inflammation may differ between genders resulting in distinct cardiac modulation.

Methods and Results: 34 HFpEF patients, who underwent cardiac catheterization and had no significant coronary artery disease, were sub-divided based on gender: 16 women vs. 18 men. More HFpEF patients were obese (P<0.05) or had diabetes mellitus (P<0.05). Left ventricular myocardial biopsies were procured transvascularly in HFpEF patients. HFpEF women showed more increased of pro-inflammatory cytokines and oxidative stress than HFpEF men. Although HFpEF women exhibit more inflammation and oxidative stress compared to HFpEF men, coronary artery dilations to acetylcholine (ACh) and sodium nitroprusside (SNP, the direct nitric oxide donor) were similar in both genders but reduced compared to the control group.

Nevertheless, cardiomyocyte passive force (F_passive) was higher in HFpEF women compared to HFpEF men due to a more significant reduction of titin phosphorylation in HFpEF women. We revealed more increased mitochondrial oxidative stress in cardiomyocytes in HFpEF women compared to men, which was associated with more impairment of the nitric oxide/soluble guanylyl cyclase/protein kinase G (NO-sGC-PKG) pathway, thereby increasing F_passive. However, we also found more deranged regulation of heat shock protein(HSP)27 and α-B-crystalline in HFpEF women compared to HFpEF men. HSP27 is a chaperone that has diverse functions, including inhibiting protein aggregation by stabilizing partially denatured proteins such as titin. Addition of HSP27 shifted the F_passive-sarcomere length relation downward making the cardiomyocyte more compliant in both genders but did more so in HFpEF men than in HFpEF women suggesting aggregation of titin in both genders, but perhaps more in HFpEF women. HSP 27 failed to fully shift the F_passive-sarcomere length relation downward to donor baselines in HFpEF women. Subsequent treatment with PKG further shifted the F_passive-sarcomere length relation downward in HFpEF women towards donor baselines. Additional, significant differences were also noted in the levels of protease enzymes, including caspase 1, caspase 3, caspase 9, and caspase 12, between men and women.

Conclusion: HFpEF women showed higher cardiomyocyte stiffness due to deranged stress pathways because of higher oxidative stress in the cardiomyocyte. High cardiomyocyte stiffness was corrected by HSP27 and PKG probably through relief of titin aggregation and phosphorylation.