Increased serum phenylalanine and tyrosine concentration related to inflammation in patients with primary angiitis of the central nervous system.

Background: Primary angiitis of the central nervous system (PACNS) is a rare disease characterized by severe central nervous system (CNS) vascular inflammation. Serum aromatic amino acids have been reported to associate with inflammation. However, the aromatic amino acids in PACNS are poorly understood. Methods: We obtained serum samples from 18 PACNS patients, 35 healthy control, and 17 other neurological diseases patients without inflammation. Serum concentrations of aromatic amino acids were assayed by a liquid chromatograph mass spectrometer (LC-MS). Inflammatory cytokine levels, including interleukin (IL)-1β, IL-6, IL-8, complement 3 (C3), C4, and tumor necrosis factor-α (TNF-α) were also collected. Results: Of aromatic amino acids, tyrosine, and phenylalanine but not tryptophan in serum were significantly elevated in PACNS patients. Notably, phenylalanine levels were positively correlated with C3, C4, and IL-8. Receiver operating characteristic (ROC) curve evidence tyrosine and phenylalanine are capable of discriminating between PACNS, HC, and OND. Conclusions: Our exploratory data suggest that elevated serum phenylalanine and tyrosine may be associated with PACNS-related inflammation. Whether these metabolites can serve as differential-diagnostic biomarkers requires validation in larger, multicentre cohorts.