https://doi.org/10.1007/s00392-025-02625-4
1Herz- und Diabeteszentrum NRW Agnes Wittenborg Institut für translationale Herz-Kreislaufforschung Bad Oeynhausen, Deutschland; 2Herz- und Diabeteszentrum NRW Allgemeine und Interventionelle Kardiologie/Angiologie Bad Oeynhausen, Deutschland; 3Universität Bielefeld Technology Platform Genomics, Center for Biotechnology (CeBiTec) Bielefeld, Deutschland; 4Universität Bochum Medical Imaging Center - Electron Microscopy Medical Analysis Bochum, Deutschland
Background: Heart failure with preserved ejection fraction (HFpEF) is a disorder with heterogenous phenotypes derived from different pathophysiological mechanisms, which might require tailored therapies. Cardiometabolic HFpEF is linked to alterations in myocardial substrate metabolism. Nitro-oleic acid (NO2-OA) is an electrophilic molecule, which has been identified to exert protective properties in various animal models and is currently tested in phase 2 trials for patients with obese asthma. In this study, we sought to investigate the effects of NO2-OA on heart failure in the ‘two-hit’ HFpEF mouse model induced by high fat diet (HFD) and endothelial nitric oxide synthase (eNOS) inhibition.
Methods and Results: HFpEF was induced by a combination of HFD and eNOS inhibition with Nω-Nitro-L-arginine methyl ester hydrochloride (L-NAME) for 15 weeks in C57BL/6N mice. At week 11, mice received either NO2-OA (HFD+L-NAME NO2-OA) or vehicle (HFD+L-NAME) via mini-osmotic pumps for 4 weeks. Control (Ctrl) mice received a chow diet. Remarkably, diastolic dysfunction was ameliorated after treatment with NO2-OA in HFD+L-NAME mice as revealed by E/é, isovolumetric relaxation time, global longitudinal strain and compliance index. Invasive pressure volume analyses confirmed these effects, left ventricular (LV) stiffness index and end-diastolic pressure were significantly increased in vehicle-treated, but not in NO2-OA-treated HFD+L-NAME mice. Not only LV dysfunction, but also heart failure symptoms were alleviated by NO2-OA. Exercise capacity was significantly impaired in HFD+L-NAME but not in HFD+L-NAME NO2-OA mice compared to Ctrl mice. Furthermore, left atrial area enlargement was blunted by NO2-OA and pulmonary artery remodeling was markedly mitigated. Treatment of HFD+L-NAME mice with oleic acid had no significant effect on cardiac function, underlining the relevance of the nitro group.
Whereas LV hypertrophy, fibrosis and systemic inflammation were not affected by NO2-OA, quantification of mitochondrial respiration in isolated cardiomyocytes from the three groups unveiled, that oxidative phosphorylation and fatty acid oxidation (FAO)-dependent respiration was significantly enhanced in NO2-OA-treated mice compared to Ctrl. Interestingly, transmission electron microscopy disclosed an increased number of mitochondria per mitochondrial area in LV sections of HFD+L-NAME NO2-OA compared to vehicle and Ctrl mice. In line with that, a proteome analysis of LV tissue displayed, that in HFD+L-NAME NO2-OA mice 27% of all identified proteins were significantly increased in hearts compared to vehicle-treated HFD+L-NAME mice. Annotation of the enriched proteins by NO2-OA identified that 25% of increased proteins were mitochondrial proteins (mitoCarta data base). Profoundly increased protein amounts of the fatty acid (FA) translocase CD36 and FA metabolizing enzymes in HFD+L-NAME NO2-OA mice, together with the increase in FAO point, towards amplified FA utilization, which might compensate a potential energy deficit in HFpEF hearts. Immunoblot analyses revealed that NO2-OA induced an activation of the AMP-dependent protein kinase (AMPK), which is known to activate catabolic pathways and mitochondrial biogenesis.
Conclusion: Treatment of HFpEF mice with NO2-OA eliminates diastolic dysfunction and alleviates heart failure symptoms. This effect is linked to enhanced fatty acid metabolism due to altered mitochondrial composition.