Plasma and Liver Metabolic Profiles in Mice Subjected to Subchronic and Mild Social Defeat Stress

To improve the quality of life of
animals, understanding of stress-induced
changes is necessary. Previously, we established a subchronic and
mild social defeat stress (sCSDS) model in mice, which showed significantly
higher body weight gain, food intake, and water intake compared to
control mice. In this study, we elucidated metabolic profiles of plasma,
liver, and urine in sCSDS mice by using metabolome and biochemical
analyses. There was no significant difference between defeated and
control mice in the plasma metabolites. In the liver of sCSDS mice,
levels of taurocyamine (GES), phosphorylcholine, d-alanyl-d-alanine (d-ala-d-ala), and 1-methylnicotinamide
(MNA) were elevated compared to controls. Taurine plays a role in
osmotic regulation, and GES is a potential inhibitor of the taurine
transporter. The polydipsia and increased body water content in sCSDS
mice may disrupt body fluid balance following GES elevation. Furthermore,
sCSDS increased heart and spleen weight significantly. Because MNA
and d-ala-d-ala have anti-inflammatory and hepatoprotective
effects, they may reduce inflammation in the liver of sCSDS mice.
Finally, suppressed excretion of urine sodium was observed in sCSDS
mice. Therefore, sCSDS induces various changes in metabolite concentrations,
especially related to osmoregulation and inflammation, that may be
used as biomarkers for stress-induced changes in animals.