Transcriptomic profiling study of canine degenerative mitral valve disease

Degenerative mitral valve disease (DMVD) is the most common cardiac disease in dogs. Some signaling pathways have been implicated in DMVD, including the serotonin and TGF-beta pathways. We sought to identify additional molecular and metabolic pathways that contribute to DMVD using transcriptomic and metabolomic studies. RNA-seq gene expression evaluated on total RNA isolated from left ventricle (LV) and mitral valve (MV) identified 812 differentially expressed transcripts (DETs) in LV and 263 DETs in MV. Out of 15 transcripts selected for RT-qPCR validation, we confirmed 13. In addition, serum samples were collected for metabolomic evaluation. Endothelial nitric oxide synthase (eNOS) was significantly up-regulated in both LV and MV while the level of circulating asymmetrical dimethyl arginine (ADMA), an endogenous NOS inhibitor, was lower in DMVD. Expressions of matrix metalloproteinases (MMP) and their endogenous inhibitor tissue inhibitor of matrix metallopeptidases (TIMP) were altered. This study demonstrates transcript and metabolite differences consistent with increased nitric oxide (NO) and reactive oxygen species (ROS) production, impaired fatty acid transport and oxidation, and increased glucose uptake and glycolysis in DMVD. Our findings are consistent with metabolic conversion in the DMVD heart from oxidative metabolism to glycolysis along with an increased concentration of NO and ROS activity suggesting an alternative signaling effect. Alterations of redox-sensitive NO signaling may play a role in ECM (ECM) homeostasis via modulating MMP and TIMP expression. mRNA profiles of both left ventricle and mitral valve tissues from dogs with DMVD and healthy controls were generated by deep sequencing approach using Illumina HiSeq 2000 platform.