Kynurenine pathway metabolites are increased in inflammatory depression and decrease with omega-3 treatment

Activation of the kynurenine pathway (KP) with resulting accumulation of neuroactive metabolites may be a downstream pathophysiological mechanism in inflammatory depression. The aims of this study were to investigate KP metabolites in inflammatory depression compared to non-inflammatory depression and healthy controls, and whether these metabolites change with nutraceutical interventions with potential KP-modulating effects. We combined data from two antidepressant clinical trials: one with omega-3 polyunsaturated fatty acids (n-3 PUFAs) and one with a Limosilactobacillus reuteri probiotic supplement as the active intervention. Patients with Major Depressive Disorder (MDD) (n=170) were stratified at baseline according to high-sensitivity C-reactive protein (hs-CRP) levels into an inflammatory (hs-CRP ≥1 mg/L, n=127) and a non-inflammatory (hs-CRP