Constitutive loss of kynurenine-3-monooxygenase changes circulating kynurenine metabolites without affecting systemic energy metabolism

The kynurenine pathway of tryptophan degradation is influenced by metabolic stressors: exercise raises circulating KYNA levels, while obesity is linked to increased QUIN. We investigated whether a mouse model lacking KMO—leading to increased circulating KYNA and decreased QUIN—would exhibit changes in energy metabolism. We found that energy metabolism was largely unaffected despite robust changes in circulating kynurenine metabolites, suggesting that systemic KMO inhibition may not have widespread metabolic effects.