NPPB and obesity due to melanocortin 4 receptor deficiency: LXRs may play a regulatory role in natriuretic peptide expression since Anp and Bnp mRNA levels are significantly increased by 2.8-fold and 3.0-fold, respectively, in mice with cardiac-specific LXRα overexpression (described previously, [17]), and remain upregulated in the presence of HFD-induced obesity (Fig. 2f, g).