Taurine and Epidermal Growth Factor Belong to the Signature of First-Episode Psychosis

Abstract

This study evaluated the levels of two amino acid derivatives taurine and spermine in first-episode psychosis (FEP) patients and their response to antipsychotic treatment. The levels of taurine and spermine were significantly up-regulated in antipsychotic-naïve FEP patients compared to control subjects (CS). Treatment of FEP patients with antipsychotic drugs significantly reduced the positive symptoms of schizophrenia. This positive effect was accompanied by a significant reduction of taurine and spermine to the levels measured in CS. General linear model was used to establish associations of taurine and spermine with the levels of cytokines and growth factors, measured in our previous experiments using the same study sample. There was a strong association between taurine and epidermal growth factor (EGF). Both biomarkers significantly correlated with the disease symptoms as well as with the effectiveness of antipsychotic treatment. Accordingly one can conclude that taurine and EGF belong to the signature of FEP. Most probably they reflect altered oxidative stress and corrupted function of N-methyl-D-aspartate (NMDA) receptors in FEP.

Profiling of Amino Acids and Their Derivatives Biogenic Amines Before and After Antipsychotic Treatment in First-Episode Psychosis

“…Taking into account the possible interaction of AAA with Kyn metabolism one may suggest that the reduction of their levels in drug-naïve FEP patients compared to CSs may indirectly reflect the imbalance in Kyn pathways. Furthermore, altered levels of Kyn seem to be in line with our previous findings with the elevation of pro-inflammatory cytokines, EGF and taurine, which possibly reflect the corrupted function of NMDA receptors in FEP patients [ 27 , 31 ].…”

“…Under the treatment the levels of taurine elevated by FEP were reduced to the respective values in CSs and the similar inhibition was determined for spermine as it was established in our previous study [ 27 ]. The circulating levels of alpha-AAA and Kyn were also elevated to the level of CSs with the antipsychotic treatment.…”

“…Taurine and spermine target the GluN2B-containing NMDA receptor subtype [ 51 , 53 ]. Previously, using the same cohort of participants we demonstrated strong positive link between elevated levels of taurine, spermine, epidermal growth factor (EGF) and particular inflammatory marker levels on FEP and 7-months treatment outcome [ 27 ]. Moreover, the clinical study performed by Samuelsson and colleagues (2013) [ 54 ] demonstrated significantly elevated plasma levels of taurine in patients suffering from chronic SCH and a recent research where taurine was used as the adjunctive therapy to antipsychotic treatment revealed some beneficial effects in FEP patients [ 55 ].…”

“…The protocol was approved by the Ethics Review Committee on Human Research of the University of Tartu (Estonia). Both FEP and CSs groups were identical and subjected to the versatile characterization by previous studies [ 27 , 28 , 31 – 33 ].…”

“…So far the existing studies demonstrated altered levels of Glu [ 23 ] and Hcy [ 24 , 25 ] in FEP, and also higher levels of Asp, citrulline (Citr), Phe, and lower serum levels of Tyr, Trp, and the ratio of Trp to the competing AAs in drug-free (including drug-naïve) SCH patients compared to control subjects (CSs) [ 26 ]. Recently, we established significant shift in blood levels of taurine and spermine in FEP patients [ 27 ], and that levels of methionine sulfoxide (Met-So) and methionine (Met) did not differ between antipsychotic-naïve FEP patients and individuals without a history of psychiatric disorders [ 28 ]. However, with regard to serum levels of oxidative stress parameters, existing literature provides rather conflicting evidence [ 12 ].…”