Increased plasma level of kynurenic acid in drug-free patients with first-episode schizophrenia compared to patients with chronic schizophrenia and healthy controls: preliminary data

Abstract

Background

Kynurenic acid (KYNA) is a metabolite of tryptophan (TRP). KYNA levels have been reported with controversial findings in patients with schizophrenia.

Aim

This study aimed to investigate the probable effects of medication and illness chronicity on peripheral KYNA levels in schizophrenia.

Methods

We assessed peripheral (plasma) TRP metabolite levels in 38 drug-free patients with first-episode schizophrenia (FES), 65 patients with chronic schizophrenia (CHS), and 70 healthy controls by using high-performance liquid chromatography–tandem mass spectrometry (LC-MS/MS). The symptom severity of patients was evaluated by using the Positive and Negative Syndrome Scale (PANSS). Finally, we analyzed the association of TRP metabolites with symptom severity.

Results

We found significantly higher KYNA levels in FES patients than in both healthy controls (p < 0.01) and CHS patients (p < 0.05). No significant association was observed between plasma TRP metabolite levels and PANSS scores in either FES or CHS patients.

Conclusions

In conclusion, elevated plasma KYNA levels may be a promising biomarker in FES patients. Medication and illness chronicity may affect peripheral KYNA levels with a currently unknown mechanism.

Keywords:

• Schizophrenia
• kynurenic acid
• chronicity
• symptom

Disclosure statement

All authors declare no potential conflicts of interest.

Author contributions

Yuping Ning led the overall design and contributed to revising the manuscript. Fengchun Wu, Sumiao Zhou, and Hehua Li conducted the study. Runhua Wang contributed to language polishing. Wenhua Ding performed statistical analyses and wrote the first draft of the manuscript. All authors contributed to and approved the final manuscript.

Additional information

Funding

This study was supported by the Science and Technology Plan Project of Guangdong Province (2019B030316001), the China Postdoctoral Science Foundation (2018M640769), the Natural Science Foundation of Guangdong Province (2020A1515010077), and the Scientific Research Project of Traditional Chinese Medicine of Guangdong (20211306).

Notes on contributors

Wenhua Ding

Wenhua Ding is a Chinese psychiatrist and Ph.D. in the Affiliated Brain Hospital of Guangzhou Medical University, Guangzhou, Guangdong, China.

Fengchun Wu

Fengchun Wu is a Chinese psychiatrist in the Affiliated Brain Hospital of Guangzhou Medical University, Guangzhou, Guangdong, China.

Sumiao Zhou

Sumiao Zhou is a Chinese psychiatrist in the Affiliated Brain Hospital of Guangzhou Medical University, Guangzhou, Guangdong, China.

Hehua Li

Hehua Li is a Chinese psychiatrist in the Affiliated Brain Hospital of Guangzhou Medical University, Guangzhou, Guangdong, China.

Runhua Wang

Runhua Wang is a Chinese psychiatrist and Ph.D. in the Affiliated Brain Hospital of Guangzhou Medical University, Guangzhou, Guangdong, China.

Yuping Ning

Yuping Ning is a Chinese psychiatrist and Ph.D. in the Affiliated Brain Hospital of Guangzhou Medical University, Guangzhou, Guangdong, China. Also, she works in the first School of Clinical Medicine, Southern Medical University, Guangzhou, Guangdong, China.