| The study evaluated whether the activity of the indoleamine 2,3 dioxygenase (IDO) enzyme is increased post-stroke and contributes to the development of post-stroke depression (PSD) via tryptophan (TRP) depletion and neurotoxic kynurenine (KYN) metabolite production. The activity of IDO was measured using the KYN/TRP ratio. Participants were assessed for depression severity using the Center for Epidemiological Studies Depression Scale (CES-D). Blood TRP, KYN, large neutral amino acids and cytokines were measured and compared. Fifty-four (mean age=69.9+/-15.2, male=52.7%, mean NIHSS=7.3+/-4.6) patients within 28.9+/-40.3 days of stroke were separated into two groups: non-depressed (n=38, CES-D= 6.1+/-4.9) and those with significant depressive symptoms (n=16, CES-D=26.8+/-10.8). Higher mean KYN/TRP ratios were demonstrated in stroke patients with depressive symptoms (non-depressed= 69.3+/-36.9 vs. depressive symptoms=78.3+/-42.0, F3,50=4.61, p=0.006) after controlling for LNAA (p=0.026) and hypertension (p=0.039). As the KYN/TRP ratio reflects decreased TRP and increased neurotoxic KYN metabolites, both mechanisms may play an etiological role in PSD. |
