There were no significant differences in the levels of propionic acid and FFAR2 in the primary biopsies between non-IBD patients and IBD patient (UC, CD) groups, except for a down-regulation of butyric acid in UC and CD, and valerate/isovalerate in UC samples, suggesting an inactive state for these microenvironmental components in primary samples (Fig. 6A and B). Here, FFAR2 is linked to inflammatory bowel disease.