Clin Res Cardiol (2022). https://doi.org/10.1007/s00392-022-02002-5

Unbiased screen of the cardiac proteome in a rat HFpEF model reveals key pathway changes due to obesity

F. Koser1, M. Abdellatif2, C. Türk3, A. J. Hobbach4, H. Reinecke4, M. Krüger3, S. Sedej2, W. A. Linke1

1Institute of Physiology II, University Hospital Münster, Münster; 2Division of Cardiology, Medical University of Graz, Graz, Österreich; 3Institute for Genetics, University of Cologne, Cologne; 4Department of Cardiology I, University Hospital Münster, Münster;

Background: Despite the high public-health burden, the pathomechanism of heart failure with preserved ejection fraction (HFpEF) remains elusive and evidence-based therapies are lacking. Diastolic dysfunction is a key feature in HFpEF patients, caused in part by increased stiffness of the cardiomyocyte protein titin. The current paradigm of HFpEF pathophysiology postulates meta-inflammation and oxidative stress as crucial disease triggers, resulting from a combination of metabolic syndrome and hypertension. Good patient-mimicking animal models of HFpEF are sparse but one of the few established models is the Zucker diabetic fatty/Spontaneous hypertensive heart failure F1 hybrid (ZSF1) rat, which does have hypertension and metabolic syndrome. The ZSF1 rat is available as a lean (no HFpEF) and an obese variant (HFpEF), which have almost the same genetic background. Objective: To test how the presence of obesity alters protein expression and function in the hearts of ZSF1-obese versus ZSF1-lean rats, and to gain new insights into the HFpEF pathomechanism using unbiased mass spectrometry-based proteomic screens, as well as immunoblotting. Methods & Results: Eight-week-old female and male ZSF1-obese and ZSF1-lean rats were fed with a Purina diet until the onset of the HFpEF phenotype in the ZSF1-obese animals at around 20 weeks of age. Mass spectrometric analyses of heart tissue samples showed that the cardiac proteome and phosphoproteome in ZSF1-obese versus ZSF1-lean were less markedly altered than the acetylome. Many acetylation changes affected proteins involved in cardiac metabolism and energy production, suggesting obesity as a crucial comorbidity in the HFpEF pathogenesis. Some of the proposed key features of the HFpEF pathomechanism could be confirmed in ZSF1-obese rats by immunoblot-based quantitation, while others could not. Unexpectedly, both eNos activity and iNos expression (markers of oxidative/nitrosative stress) were unaltered in ZSF1-obese hearts, as was the phospho-Ire1α:Ire1α ratio (indicating Ire1α activity), a measure of the unfolded protein response pathway. In contrast, CD68 and P-selectin expression were increased in ZSF1-obese versus ZSF1-lean, indicating macrophage infiltration and microvascular endothelial inflammation. Moreover, PKG activity and PKG site-specific titin phosphorylation in the N2Bus segment were decreased in the hearts of ZSF1-obese rats, consistent with increased titin-based cardiomyocyte stiffness. In addition, titin showed several hypo-acetylated sites in ZSF1-obese versus ZSF1-lean hearts, which could also alter titin-based stiffness. Disturbed Ca2+-handling in ZSF1-obese hearts was evidenced by altered posttranslational modifications of the ryanodine receptor (hyper-phosphorylated) and SERCA (hyper-acetylated). Conclusion: Our findings suggest that obesity on the background of hypertension and additional co-morbidities triggers crucial proteomic and posttranslational alterations in HFpEF hearts, which lead to meta-inflammation and cardiomyocyte stiffening. Altered acetylation of multiple cardiac proteins caused by obesity could be a key posttranslational modification in HFpEF.

https://dgk.org/kongress_programme/jt2022/aP816.html