HFpEF is a multifactorial systemic disease, characterized by cardiac structural remodeling and an inadequate augmentation of cardiac contractile function upon physiological stress. CM contractile function at baseline and its functional contractile reserve are regulated by compartmentalization of the main second messengers, cAMP and Ca2+, in highly controlled intracellular functional microdomains. We hypothesize that HFpEF is associated with molecular-level alterations in intracellular cAMP- and Ca2+ signaling microdomains, which limit the functional reserve of the CM. We aim at establishing alterations of β-adrenoreceptor -subtype /cAMP- and Ca2+ dynamics and the impact on the functional reserve with physiological inotropic stimuli (adrenergic, frequency, stretch) in metabolic vs non-metabolic HFpEF. In addition, we investigate the effects of acute metabolic stress on the cardiomyocyte functional reserve in HFpEF and explore underlying mechanisms.

Graphical Abstract Murine cardiomyocytes isolated from HFpEF wt and HFpEF hearts, with and without stimulation by exercise, will be phenotyped. New fluorescent compounds and advanced fluorescence microscopy will allow assessing changes to subcellular compartmentalization of cAMP and intracellular calcium handling. Mass spectrometry will bes used to reveal alterations of the relevant proteome.