On the other hand, loss of ET, due to for example, mutation or knockout of octn1 gene encoding organic cation/carnitine transporter 1 (OCTN1) that exclusively transports ET across intestinal epithelia, is associated with increased risks of inflammatory diseases such as rheumatoid arthritis (RA) and Crohn’s disease [59,60]. Here, SLC22A4 is linked to Crohn disease.