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.