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

Pediatric dilated cardiomyopathy (DCM) is a devastating and poorly understood disease with most clinical treatment paradigms extrapolated from the adult population. Our studies have demonstrated that aspects of metabolism and mitochondrial function are dysregulated in pediatric DCM hearts. Cardiolipin (CL), a unique phospholipid in the inner mitochondrial membrane, is essential for optimal mitochondrial function and was shown to be dysregulated in both the failing adult and pediatric human heart. The objective of this study is to investigate if serum circulating factors from pediatric DCM patients can remodel CL resulting in mitochondrial dysfunction in vitro , 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 the Agilent Seahorse, and reactive oxygen species (ROS) was assessed using Electron Paramagnetic Resonance Spectroscopy. Relative mitochondrial DNA (mtDNA) copy number was determined by qPCR and expression of enzymes involved in CL biosynthesis and remodeling were analyzed using RT-qPCR. Mass-spectrometry 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 mtDNA copy number were not significantly altered, we show that DCM serum decreases mitochondrial function, which is associated with alterations in CL content and composition and the downregulation 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 the transcription factor PPARα. In conclusion, pediatric DCM serum circulating factors can promote CL remodeling resulting mitochondrial dysfunction in primary cardiomyocytes. These findings suggest that CL could be a novel therapeutic target for this particular population.