In addition, animal studies have shown that nonspecific inflammation can cause EC cells hyperplasia and decrease expression of SERT (Linden et al., 2003[41]), leading to an increase in 5-HT at the mucosal level and followed by the incremental gut motility and secretion, thereby causing IBS symptoms (Dunlop et al., 2005[13]). Here, SLC6A4 is linked to irritable bowel syndrome.