Elevated levels of TDO and IDO-1 mRNA was observed in 6–8 month 3xTg AD cerebellum compared to age matched controls (1.8-fold and 1.7-fold, respectively) and in 10–12 month mice (2.2-fold and 1.5-fold, respectively), but the difference was statistically significant only for TDO mRNA expression (p<0.01 for 6–8 month, p<0.001 for 10–12 month). Here, TDO2 is linked to Alzheimer disease.