Microbial regulation of SAA3 expression in mouse colon and adipose tissue.

Recently, we demonstrated that colonic and adipose expression of SAA3 was modulated by the gut microbiota and Toll-like receptor signaling in mice. We observed that SAA3 was expressed by colonic epithelial cells and that its expression was induced in a murine colonocyte cell line following lipopolysaccharide stimulation and nuclear NFκB translocation. In this addendum, we extend this initial study and suggest that SAA3 (1) resembles human SAA1 both in amino acid homology and tissue distribution, (2) appears to have autocrine or paracrine effects rather than endocrine, and (3) binds to bacteria within the gastrointestinal tract. Although speculative, these observations raise the possibility that SAA3 may promote local inflammation in adipose tissue that affects insulin signaling and also function as an antimicrobial agent in the colon.