Background: Major depressive disorder (MDD) is a common psychological disorder
worldwide. However, one-third of patients with MDD are resistant to the present anti-depressant
medicine, which regulates monoamine contents in the brain. Thus, another drug target is strongly
required. Much evidence strongly suggests that sirtuin1, which is the key factor in regulating the
mitochondrial activity, may be implicated in MDD.
Objective: Since it is suggested that royal jelly (RJ) ameliorated depressive-like behavior and affected
mitochondrial activity in mice, we hypothesized that RJ could be an alternative medicine
against MDD, which acts via sirtuin1 signaling to improve mitochondrial activity.
Methods: In the present study, we applied a mouse model of MDD to investigate the effect of RJ
on the depressive-like behavior and the sirtuin1 signaling on mitochondrial activity.
Results: Our results indicated that either the oral administration of RJ for 12 days or single intracerebroventricular
(i.c.v.) injection decreased the duration of immobility in the tail suspension test,
which suggested that RJ had an antidepressant-like effect. Moreover, sirtuin1 protein expression increased
in mice following RJ treatment in the amygdala region, but not in the other brain regions.
Similarly, the expressions of oxidative phosphorylation (OXPHOS) related proteins increased in
the amygdala regions, but not in the hippocampal regions.
Conclusion: The increase of sirtuin1 and OXPHOS protein expression may at least in part contribute
to the antidepressant-like effect of the RJ pathway, and RJ may have the potential to be a
novel anti-depressant drug.