Abstract Body (Do not enter title and authors here): Introduction/Background: Stimulation of soluble guanylate cyclase (sGC) represents a promising pharmacological strategy in the treatment of heart failure with reduced ejection fraction, but it has not been proved yet to be efficacious in heart failure with preserved ejection fraction (HFpEF).
Research Questions/Hypothesis: Our aim was to clarify the molecular pathways involved in the cardiac effects of sGC stimulation in a preclinical model of early-stage HFpEF through the analysis of proteomic/phosphoproteomic profiles.
Methods/Approach: Male obese ‘Zucker fatty and spontaneously hypertensive’ (ZSF1) rats (n=10) were treated at 14 weeks of age for 4 weeks with the sGC stimulator vericiguat at 3 mg/kg/p.o. once daily. Control groups (obese and lean ZSF1 rats, n=10) received vehicle. Echocardiographic evaluation was performed at 17 weeks of age. Oxygen consumption rate of left ventricle mitochondria was assessed by high-resolution respirometry. Left ventricle tissue samples were examined under electron microscopy, and proteomic/phosphoproteomic profiling was performed on a TripleTOF® 6600 LC-MS/MS system. Statisticals: Mann-Whitney/Chi-squared Tests.
Results/Data: sGC stimulation improved diastolic function in treated rats, markedly enhancing cardiac mitochondrial respiration and cristae organization. Proteomic analysis comparing obese treated group vs. obese control group determined statistically significant differences of 88 proteins in left ventricular tissue. Treatment boosted biological processes related to mitochondrial function, oxidative phosphorylation, respiratory electron chain or generation of ATP, and decreased myofibrillar remodeling pathways. Phosphoproteomic profile revealed 49 phosphoproteins whose levels were significantly different between groups. Treatment increased phosphoproteins involved in pentose phosphate shunt, and small molecule, carboxylic, lipid and monocarboxyl acid catabolic pathways, while diminished those correlated with cytoskeleton-dependent cytokinesis, protein folding and organelle, membrane and vesicle fusion processes.
Conclusion(s): Our data provides molecular insights into the potential role of sGC stimulation in regulating cardiac mitochondrial respiration and cristae morphology in early-stage HFpEF. Several relevant changes in proteomic/phosphoproteomic profiles define the mitochondrial respirasome as the biological process most affected at cardiac level after sGC stimulation.