Research PaperPhoenixin is negatively associated with anxiety in obese men

- Phoenixin is a recently discovered peptide initially implicated in reproduction.
- Phoenixin was also shown to have an anxiolytic effect in mice.
- Phoenixin is detectable in the circulation in humans.
- Phoenixin shows a negative association with anxiety in obese men.
- Phoenixin might be an interesting target in the treatment of anxiety disorders.

Phoenixin was recently identified in the rat hypothalamus and initially implicated in reproductive functions. A subsequent study described an anxiolytic effect of the peptide. The aim of the study was to investigate a possible association of circulating phoenixin with anxiety in humans. We therefore enrolled 68 inpatients with a broad spectrum of psychometrically measured anxiety (GAD-7). We investigated men since a menstrual cycle dependency of phoenixin has been assumed. Obese subjects were enrolled since they often report psychological comorbidities. In addition, we also assessed depressiveness (PHQ-9) and perceived stress (PSQ-20). Plasma phoenixin levels were measured using a commercial ELISA. First, we validated the ELISA kit performing a spike-and-recovery experiment showing a variance of 6.7 ± 8.8% compared to the expected concentrations over the whole range of concentrations assessed, while a lower variation of 1.6 ± 0.8% was observed in the linear range of the assay (0.07-2.1 ng/ml). We detected phoenixin in the circulation of obese men at levels of 0.68 ± 0.50 ng/ml. These levels showed a negative association with anxiety scores (r = −0.259, p = 0.043), while no additional associations with other psychometric parameters were observed. In summary, phoenixin is present in the human circulation and negatively associated with anxiety in obese men, a population often to report comorbid anxiety.