Serum from pediatric dilated cardiomyopathy patients promotes dysregulation of cardiolipin biosynthesis and mitochondrial dysfunction

Abstract

Pediatric dilated cardiomyopathy (DCM) is a devastating and poorly understood disease with most clinical treatment paradigms extrapolated from the adult population. Our studies showed that aspects of metabolism and mitochondria function are dysregulated in pediatric hearts. Cardiolipin (CL), a unique phospholipid in the inner mitochondrial membrane, is essential for optimal mitochondrial function and was shown to be dysregulated in failing adult hearts. We investigate if serum circulating factors from pediatric DCM patients can remodel CL resulting in mitochondrial dysfunction similar to what is observed in the failing pediatric heart. Using a novel in vitro model that consists of treating neonatal rat ventricular myocytes (NRVMs) with serum from pediatric DCM patients or from non-failing (NF) healthy controls, mitochondrial respiration was assessed using Seahorse assay, and reactive oxygen species (ROS) was assessed using Electron Paramagnetic Resonance Spectroscopy. Expression of enzymes involved in CL biosynthesis and remodeling were analyzed using RT-qPCR and relative mtDNA copy number determined by qPCR. Mass spectroscopy was used to quantitate total and specific CL species and to investigate the metabolite composition of NRVMs treated with NF or DCM serum. While mitochondrial ROS and copy number were not significantly altered, we showed that DCM serum decreases mitochondrial function, which is associated with alterations in CL content and composition and gene expression of enzymes implicated in CL biosynthesis and remodeling. Analysis of metabolite content showed an alteration of pathways involved in fatty acid metabolism, mitochondrial biogenesis and regulation of β-oxidation by PPARα. Pediatric DCM serum circulating factors can promote CL remodeling resulting in mitochondrial dysfunction in cardiomyocytes. These findings suggest that CL could be a therapeutic target for this particular population.