SLC22A4 encodes OCTN1, a membrane transporter mediating sodium-dependent uptake of ergothioneine, a food-derived antioxidant found in mushrooms and fermented foods, as well as acetylcholine and carnitine. The transporter is expressed on the apical membrane of the small intestine and functions in ergothioneine absorption and renal reabsorption, accumulating preferentially in tissues subject to oxidative stress 1. SLC22A4 exhibits a general physiological role linked to better survival by controlling inflammation and oxidative stress. Knockout models show increased susceptibility to oxidative stress and inflammation 2. In humans, blood ergothioneine levels decline after age 60, with lower levels associated with more rapid cognitive decline, whereas high plasma ergothioneine correlates with reduced cardiovascular and overall mortality 2. In the brain, OCTN1-mediated ergothioneine transport supports antidepressant effects, enhanced memory, and protection against stress-induced sleep disturbance and amyloid-β neuronal injury 3. SLC22A4 has been implicated in multiple inflammatory and metabolic conditions. Genetic variants associate with altered hypertension-specific mortality risk 4, and OCTN1 loss influences dysbiosis and modulates response to infliximab in colitis models 5. Recent machine learning studies identified SLC22A4 among candidate biomarker genes for acute myocardial infarction risk 6 and as an immune-related signature in ischemic stroke 7. However, SLC22A4 polymorphisms show population-specific disease associations, with limited evidence in Chinese Han populations for Crohn's disease susceptibility 8.