MK-4 is a ligand for SXR (known as its murine ortholog, pregnane X receptor, PXR) (168–170), and PXR is abundantly expressed in the intestine and liver in mammals (171); its activation suppresses the NFκB signal pathway and relieves the severity of IBD, indicating the fundamental role for PXR in IBD treatment (172, 173). The gene discussed is NR1I2; the disease is inflammatory bowel disease.