Background: Diabetes may cause cardiomyopathy characterized by cardiac fibrosis. Recent studies of genetically modified mice have elucidated a role of the natriuretic peptides (NP), type-A and type-B (ANP and BNP), and their common receptor [natriuretic peptide receptor (NPR), type-A] in development of cardiac fibrosis. The role of NP type-C (CNP) and NPR type-B (NPR-B) in the heart is less well established. In this study we examined if diabetes alters heart expression of the genes encoding the NP and its receptors.
Materials and methods: Cardiac mRNA was quantified by real-time PCR in diabetic streptozotocin (STZ)-treated and ob/ob-mice and nondiabetic control mice.
Results: The ob/ob-mice with type-II diabetes displayed highly significant increases of the cardiac mRNA expression of NPR-B and NPR-C while the expression levels of NPR-A, ANP, BNP, and CNP mRNA were similar in ob/ob-mice and controls. Mice with STZ-induced type-I diabetes also showed an increase of heart NPR-B mRNA expression at 12 weeks, but not at 3, 6 or 9 weeks after STZ-treatment. The ANP and NPR-C mRNA expressions were only altered after 3 weeks, whereas BNP, CNP and NPR-A mRNA expressions were not altered in STZ-treated-mouse hearts at any of the time points.
Conclusions: The results show that diabetes in mice confers increased NPR-B gene expression in the heart, suggesting that increased NPR-B signalling may affect development of diabetic cardiomyopathy.