Royal jelly reduces depression-like behavior through possible effects on adrenal steroidogenesis in a murine model of unpredictable chronic mild stress.

Royal jelly (RJ) is used as a dietary supplement for human health promotion. Recently, a clinical trial has reported that RJ improved mental health. The present study was conducted to experimentally support the clinical effect of RJ on mental health and to further elucidate the mechanisms of action of RJ. RJ and an ethanol extract of RJ, which contains fatty acids but not proteins, inhibited an unpredictable chronic mild stress (UCMS)-induced increase in immobility time, a depression-like behavior, in the tail suspension test. DNA microarray analysis of the adrenal grand revealed that the expression of genes involved in cholesterol metabolism was up-regulated in response to UCMS exposure and that RJ suppressed expression of genes related to cholesterol synthesis and transport. These results suggested that RJ improves stress-induced depression-like behavior by regulating adrenal steroidogenesis and that fatty acids contained in RJ partly contribute to the antidepressant effect of RJ.