Urinary metabolic disturbance in the olfactory bulbectomized rats and the modulatory effects of fluoxetine.

Aims: The present study aims to investigate the impacts of olfactory bulbectomy (OBX) on urinary metabolic profile and tryptophan metabolites in prefrontal cortex (PFC) of rats, and to explore the regulation effects of fluoxetine.

Main Methods: OBX model was developed by aspiration of olfactory bulbs. After fluoxetine treatment (10 mg/kg) for 14 days, urine samples were collected and behavior tests were applied. Tryptophan (TRP) metabolites and neurotransmitters in PFC were determined by prominence ultrafast liquid chromatography-QTRAP-mass spectrometry, and tryptophan hydroxylase 2 (TPH2) and indoleamine-2,3-dioxygenase 1 (IDO1) were evaluated by western blot. Urinary metabolites were analyzed by ultra-performance liquid chromatography coupled with quadrupole time-of-flight mass spectrometry-based metabonomics strategy.

Key Finding: OBX rats showed hyperlocomotion in open field, hyperactivity in open arm and despair status, and fluoxetine reserved these behavioral abnormalities. The levels of TRP, 5-HIAA, 5-HIAA/5-HT ratio and DA increased, while kynurenine and 5-HT decreased in PFC of OBX rats. The activities of TPH2 and IDO1were inhibited after OBX. Twenty-six altered metabolites were identified as potential biomarkers in OBX rats involved in tryptophan metabolism, gut microbiota metabolism, energy metabolism, purine metabolism, ascorbate and aldarate metabolism, and tyrosine metabolism. Among them, 15 abnormal metabolites were corrected by fluoxetine to some extent.

Significance: Our results revealed that urinary metabolic profile changed greatly in OBX rats, and identified biomarkers might be helpful for the diagnosis of agitated depression. The regulation effects of fluoxetine on urinary metabolic profile and tryptophan metabolites in PFC might contribute to its antidepressant action in OBX rats.