As shown in Fig. 2A, Saa3 gene expression in adipose tissue was significantly increased in db/db mice compared with that in db/+ mice as well as mRNA of macrophage marker genes such as Emr1 and Mpeg1. We also performed quantitative RT-PCR analysis of the expression level of the Saa3 gene in adipose tissue of mice with diet-induced obesity. This evidence concerns the gene MPEG1 and obesity due to melanocortin 4 receptor deficiency.