Inhibiting atrial natriuretic peptide clearance reduces myocardial fibrosis and improves cardiac function in diabetic rats.

AIMS: Natriuretic peptides (NPs) exert pleiotropic effects through the recruitment of cyclic guanosine monophosphate (cGMP) signalling pathways depending on their bioavailability, which is regulated by clearance receptors and peptidases. Here, we tested the hypothesis that increasing myocardial bioavailability of NP has a beneficial effect on heart failure. We studied the effects of a mutated NP, M-atrial natriuretic peptide (MANP), resistant to neprilysin in a model of diabetic cardiomyopathy characterized by marked myocardial fibrosis. METHODS AND RESULTS: Natriuretic peptides as well as sacubitril were delivered via osmotic mini-pumps to high-fat/streptozotocin-induced Type 2 diabetic (T2D) rats. Cardiac function was evaluated by echocardiography. Myocardial remodelling was studied by histological approaches, collagen phenotype, and atrial natriuretic peptide (ANP)/cGMP concentrations. Live-cell cGMP biosensing was conducted on cultured rat cardiac fibroblasts to investigate the biological effects of NP. Cyclic guanosine monophosphate signalling pathway was studied using multiple antibody arrays and biochemical assays in cardiac tissue and cultured fibroblasts. M-atrial natriuretic peptide exhibits superior efficacy than ANP in reducing left ventricular dysfunction and myocardial fibrosis with less extracellular matrix deposition. In vitro, MANP and ANP similarly generated cGMP and activated the protein kinase G (PKG) signalling pathway in cardiac fibroblasts, attenuating Mothers against decapentaplegic homolog 2 (SMAD) activation, collagen secretion, and cell proliferation. Nevertheless, in vivo, MANP specifically enhanced cardiac cGMP accumulation and was more potent than ANP in activating myocardial cGMP/PKG signalling and inhibiting the profibrotic SMAD, extracellular signal-regulated kinases 1/2, and nuclear factor of activated T cells 3 pathways. Endopeptidase inhibition using sacubitril also led to cardiac ANP/cGMP accumulation and reduced myocardial fibrosis. CONCLUSION: Myocardial bioavailability of ANP is a major determinant of peptide efficacy in reducing cardiac fibrosis and improving pump function during diabetic cardiomyopathy.