Irisin ameliorates depressive-like behaviors in rats by regulating energy metabolism.

Depression is a common psychiatric disorder that affects millions of people around the world, however, little is known about the pathophysiology of depression and the therapeutic strategy for anti-depression. In this study, we investigated the role of irisin, a regulator of energy metabolism, in the modulation of depressive-like behaviors in chronic unpredictable stress (CUS) exposed rats. ELISA showed that irisin was aberrantly regulated by CUS in the prefrontal cortex tissues and cerebrospinal fluid (CSF) of rats. CUS-induced behavioral deficits in rats were reversed by injection treatment with recombinant irisin in a dose dependent manner. Treatment with irisin at concentrations of 100 ng/ml or higher significantly increased the sucrose preference and reduced the immobility time in CUS rats. Additionally, irisin treatment also increased the activities of mitochondrial complexes I, II and IV as well as creatine kinase, which were inhibited by CUS in the prefrontal cortex of rats. We then confirmed that irisin significantly increased the levels of glucose transport and phosphorylation, as reflected by the increased type I and type II hexokinase (Hx-1 and Hx-2) and GLUT-4 as well as the ATP level in vivo and vitro. Further studies indicated that AMPK pathway was involved in the regulation of irisin on depressive-like behaviors in CUS rats. In conclusion, we demonstrated that irisin has a crucial role in inducing antidepressant-like effects in CUS rats by regulating energy metabolism in the prefrontal cortex of brain, which may provide a new insight into the biological mechanism of depression.