INTRODUCTION: Diastolic heart failure (HF) i.e., HF with preserved ejection fraction (HFpEF) accounts for ~50% of all clinical HF presentations; but unlike systolic HF i.e., HF with reduced ejection fraction (HFrEF), there are no evidenced based therapies. Obesity is commonly associated with HFpEF. However, there exist a sub-group of obese patients that exhibit a higher survival rate to HFpEF as compared to average patients. Hypertension is the most important risk factor for HFpEF, with a prevalence of 60-89% reported by large controlled trials, epidemiological studies and HF registries. HFpEF morbidity and mortality rates are staggering: 50-60% 5 year mortality rate, 50% 6 month rehospitalization rate and severe clinical disability. However, there remains an incomplete mechanistic understanding about HFpEF. OBJECTIVES: We wanted to explore new pathways related to HFpEF in order to better understand the mechamisms behind its pathophysiology. To do so, we first wanted to explore the potential crosstalk between the heart and adipose tissue during HFpEF by analyzing the adipose tissue in our HFpEF model. Secondly, we sought to test the hypothesis that chronic ETA/ETB inhibition with macitentan (mac) modulates pathologic cardiac remodeling in hypertension-induced HFpEF. METHODS: Mice (20-25 g) were anesthetized, underwent uninephrectomy and received either a continuous infusion of saline (sham) or d-aldosterone (0.3 ug/hour for 4-weeks via osmotic minipumps). All mice were maintained on standard rodent chow and 1.0% sodium chloride drinking water for 4 weeks and then harvested. Second group of mice underwent the same surgical procedure and infusion. They were maintained on standard chow for 2 weeks and then each group was randomized to chow containing macitentan (30 mg/kg/day, HFpEFmac) or standard rodent chow. After 2 additional weeks, the 4 groups of mice (n=4-8/group) were harvested. Blood pressure (BP) was obtained weekly. Prior to sacrifice, body weight and echocardiography parameters (total wall thickness (TWT) and relative wall thickness (RWT)) were determined. We also obtained diastolic dysfunction parameters including deceleration time (DT), isovolumetric relaxation time (IVRT), and E/A ratio. Furthermore, we measured organ weight after harvesting the mice and obtained histological images for the adipose tissues collected. Glucose tolerance test and acute cold tolerance test were performed on HFpEF mice to determine their metabolic state. RESULTS: HFpEF mice developed hypertension, LV hypertrophy, and diastolic dysfunction. Epididymal and inguinal adipose tissue showed significantly reduced weight and adipocyte size. HFpEF mice displayed regular glucose metabolism but were not able to endure a cold tolerance test as their body temperature dropped too low. After 4 weeks, there was no difference in body weight between sham, HFpEF, shammac and HFpEFmac. As expected HFpEF increased systolic BP (117±14 vs 133±16mmHg; P=NS); macitentan did not lower systolic BP after 2 weeks in either shammac or HFpEFmac. Similarly there was no difference in systolic BP between HFpEF and HFpEFmac. Both kidney and spleen weights were increased in HFpEF but not altered by macitentan therapy. There was no change in lung congestion as measured by wet-dry lung ratio. HFpEF increased TWT (0.998±0.04 vs. 0.79±0.11 mm; P<0.01 vs. sham) and RWT (0.686± 0.10 vs. 0.476±0.05 mm; P<0.001 vs. sham) but were modulated by macitentan (HFpEF vs. HFpEFmac; P<0.05 and P<0.001, respectively). There was no difference in chamber size between HFpEF and HFpEFmac. Similarly, IVRT, DT, left ventricular ejection fraction were no different between HFpEF and and HFpEFmac. Furthermore E/A ratio was increased in HFpEF but was not affected by macitentan CONCLUSIONS: Adipose tissue collected from our HFpEF mice displayed a very different phenotype. This demonstrates that inter-tissue communication is definitely occurring between the adipose tissue and the heart. Further research is required to explore what that communication encompasses and how they can be used to improve HFpEF. Macitentan did not lower systolic BP in sham or mice with HFpEF after the development of hypertension. Diastolic dysfunction, as measured by an increased E/A ratio, was not affected by macitentan. Macitentan significantly modulated TWT and RWT after 2 weeks of therapy. It is thus plausible that macitentan may improve HFpEF by improving adverse cardiac remodeling.

Background-Pulmonary artery hypertension (PAH) is characterized by progressive vascular changes causing increased pulmonary resistance and eventual right heart failure (HF). It has been suggested that altered myocardial substrate utilization may be associated with right HF, however these changes have not yet been well characterized. The aim of this study was to evaluate in vivo right ventricular (RV) function and RV glucose and fatty acid metabolism in an experimental model of PAH using non-invasive positron emission tomography (PET) imaging and to investigate the effect of a novel endothelin receptor antagonist, Macitentan, on the development of PAH and RV energetics. Methods and Results-Severe PAH was induced in a total of 11 male Sprague-Dawley rats using a single injection of Sugen5416 followed by chronic hypoxia. The rats were then randomized to treatment or no treatment with Macitentan (30 mg/kg daily) Five and eight weeks post injection, substrate utilization was serially assessed with 2-[18F]fluoro-2-deoxyglucose (FDG) and 4-[18F]fluoro-6-thia-heptadecanoate (FTHA) PET scans for glucose and fatty acid metabolism respectively, and reported as a standardized uptake value (SUV). This data was correlated with in vivo functional measurements with echocardiography and multi gated acquisition scans. The Sugen-hypoxia (SuHx) model resulted in an increase in RV FDG uptake over 8 weeks (SUV control: 1.56 ± 0.38, week 5 SuHx: 4.06 ± 1.90, week 8 SuHx: 4.00 ± 1.60, p<0.005 between control and week 5 SuHx). RV FTHA data showed a trend towards increased uptake with onset of PAH at week 5 SuHx (SUV control: 1.50 ± 0.40, week 5 SuHx: 3.06 ± 1.10, p>0.05). Macitentan significantly decreased RV FDG uptake (SUV week 8 SuHx: 4.00 ± 1.60, week 8 SuHx +ERA: 2.54 ± 0.90, p<0.05). This was associated with improved RV ejection fraction (PAH week 8 untreated: 53.15 ± 9.9% vs PAH week 8 treated: 73.22 ± 4.8%, p<0.01) and improved pulmonary artery pressures measured by pulmonary artery acceleration time (PAH week 8 untreated: 17.32 ± 2.30 ms vs. PAH week 8 treated: 24.38 ± 3.90 ms, p<0.001). There was a strong correlation between increased pulmonary artery pressures and increased RV FDG uptake (r=0.87, p=0.001) as well as a significant inverse relationship between improved RV ejection fraction and decreased RV FDG uptake (r=-0.72, p=0.01). Conclusion-PAH is associated with metabolic changes in the RV, characterized by increased glucose uptake and a trend towards increased RV fatty acid uptake with onset of PAH. Macitentan attenuated RV FDG uptake and significantly increased RV function as well as hemodynamics compared to untreated group.

Le syndrome métabolique (SM) est associé avec une augmentation du risque de survenue d’évènements cardiovasculaires et plus particulièrement d’insuffisance cardiaque à fraction d’éjection préservée (ICFEp). L’ICFEp représente environ 50% des IC totales, cependant, à ce jour, aucun traitement n’a permis de diminuer significativement la mortalité. L’ICFEp associée au SM, bien que d’origine multifactorielle, est caractérisée par une activation du système endothélinergique, une surexpression du récepteur minéralocorticoïde ainsi qu’une dysfonction mitochondriale participant à l’établissement et au maintien de la pathologie. Nous avons évalué dans trois études distinctes les effets à court-terme (1 semaine) et long-terme (3 mois) de trois médicaments ciblant ces systèmes biologiques, sur les dysfonctions cardiovasculaires observées dans un modèle d’ICFEp associée au SM, le rat Zucker fa/fa. Ainsi nous avons utilisé un antagoniste des récepteurs de l’endothéline, le macitentan, un antagoniste du récepteur minéralocorticoide, la finérénone, ainsi que d’une molécule diminuant la dysfonction mitochondriale, l’iméglimine. Dans les trois études à court-terme nous avons retrouvé une amélioration de la dysfonction diastolique, une augmentation de la perfusion cardiaque ainsi qu’une restauration de la relaxation coronaire endothélium dépendante. Ces améliorations étaient associées à une diminution de la production d’espèces réactives de l’oxygène au niveau du ventricule gauche. Dans les trois études à long-terme nous avons obtenus les mêmes résultats sur les fonctions vasculaire et cardiaque avec au niveau structurel une diminution du collagène interstitiel cardiaque. La production d’espèces réactives de l’oxygène était également diminuée avec les trois traitements Cette étude montre que, dans un modèle d’ICFEp associée au SM, le blocage des récepteurs de l’endothéline ou du récepteur minéralocorticoide, ou la prévention de la dysfonction mitochondriale permettent d’améliorer les dysfonctions cardiaque et vasculaire probablement via une diminution du stress oxydant / Metabolic Syndrome (MS) is associated with an increase in cardiovascular adverse events and specifically with heart failure with preserved ejection fraction (HFpEF). HFpEF represents up to 50% of HF however, no treatment effective on mortality has been yet identified. MS related-HFpEF is a multifactorial syndrome in which an increase in endothelin signaling, in mineralocorticoid receptor activation as well as mitochondria dysfunction is found and participate to the pathology. The present goal of the thesis was to evaluate in three different projects the effects of short- (1 week) and long-term (3 months) treatments, each targeting one of these biological systems, on cardiovascular dysfunction observed in a rat model of MS associated HFpEF. We have chosen the endothelin receptors antagonist macitentan, the mineralocorticoid receptor antagonist finerenone and the new glucose-lowering agent imeglimin. Our results clearly show after the short-term studies an improvement in diastolic dysfunction, an increase in myocardial perfusion as well as restoration of endothelium-dependent coronary relaxation with the 3 treatments. All these improvements were associated with a decrease in left ventricular (LV) reactive oxygen species production (ROS). We obtained the same results after the long-term studies with a decrease in LV interstitial collagen deposition. ROS production was also decreased with the 3 components. This study clearly shows that in a rat model of MS related-HFpEF, blocking endothelin receptors or mineralocorticoid receptors as well as preventing mitochondrial dysfunction is associated with an improvement in cardiac and vascular dysfunctions. These improvements probably involve, among other mechanisms, a decrease in oxidative stress.