FADS1 and inflammatory bowel disease: When we compared the 598 genes that were microbiota responsive in wild-type digestive tracts with the 2741 genes that Hnf4a regulates in CV digestive tracts, we found these lists shared 295 genes that included fads2 and saa, both of which have human orthologs that are either implicated (FADS1/2) or markers (SAA) of IBD (Fig. 2C–F; Plevy et al. 2013; Costea et al. 2014).