From Systemic Inflammation to Myocardial Fibrosis

In accordance with the comorbidity-inflammation paradigm, comorbidities and especially metabolic comorbidities are presumed to drive development and severity of heart failure with preserved ejection fraction through a cascade of events ranging from systemic inflammation to myocardial fibrosis. Recently, novel experimental and clinical evidence emerged, which strengthens the validity of the inflammatory/profibrotic paradigm. This evidence consists among others of (1) myocardial infiltration by immunocompetent cells not only because of an obesity-induced metabolic load but also because of an arterial hypertension-induced hemodynamic load. The latter is sensed by components of the extracellular matrix like basal laminin, which also interact with cardiomyocyte titin; (2) expression in cardiomyocytes of inducible nitric oxide synthase because of circulating proinflammatory cytokines. This results in myocardial accumulation of degraded proteins because of a failing unfolded protein response; (3) definition by machine learning algorithms of phenogroups of patients with heart failure with preserved ejection fraction with a distinct inflammatory/profibrotic signature; (4) direct coupling in mediation analysis between comorbidities, inflammatory biomarkers, and deranged myocardial structure/function with endothelial expression of adhesion molecules already apparent in early preclinical heart failure with preserved ejection fraction (HF stage A, B). This new evidence paves the road for future heart failure with preserved ejection fraction treatments such as biologicals directed against inflammatory cytokines, stimulation of protein ubiquitylation with phosphodiesterase 1 inhibitors, correction of titin stiffness through natriuretic peptide-particulate guanylyl cyclase-PDE9 (phosphodiesterase 9) signaling and molecular/cellular regulatory mechanisms that control myocardial fibrosis.