Additionally, we also found that kynurenate, a derivate of tryptophan metabolism associated with a decreased risk of CD, was positively correlated with proteins protective against CD including MEPE, cluster of differentiation 93 (CD93), dipeptidyl peptidase-4 (DPP4), and fibroblast activation protein (FAP). The gene discussed is DPP4; the disease is Cowden disease.