Abstract
IntroductionDepression is a serious mental illness. However, a significant proportion of patients with depression fail to achieve remission with antidepressant therapies. This study was conducted to explore the antidepressant‐like effect of flaxseed oil and flour in an animal model with depression‐like behaviors induced by chronic unpredictable stress (CUS).MethodsRats were randomly divided into five groups: normal control (Sham–Sham), CUS plus saline (S‐SN), CUS plus escitalopram (S‐Esc), CUS plus flaxseeds oil (S‐FO), and CUS plus flaxseed flour (S‐FF). Behaviors were tested using sucrose preference test and forced swimming test. The serum BDNF concentration, hippocampal BDNF mRNA, and protein expression were measured by enzyme‐linked immunosorbent assay, real‐time PCR, and Western blot, respectively.ResultsThe sucrose preference rate was significantly higher in S‐FO and S‐FF rats than in S‐SN and S‐Esc rats (p < .01), and lower in S‐Esc rats than in Sham–Sham rats (p < .01). The immobility time was significantly shorter in S‐FO and S‐FF rats than in S‐SN rats (p < .01), and shorter in S‐Esc rats than in S‐SN rats (p < .01). Plasma BDNF concentrations were significantly lower in S‐FO, S‐FF, and S‐Esc rats than in Sham–Sham rats (p < .01); BDNF was lower in S‐FO, S‐FF, and S‐SN rats than in S‐Esc rats. The hippocampal BDNF protein expression was significantly higher in S‐Esc rats than in S‐SN rats (p < .05). The hippocampal BDNF mRNA expression was significantly higher in S‐Esc rats than in S‐SN rats (p < .01). The BDNF gene expression in plasma and the hippocampus negatively correlated with the immobility time (p < .05), but BDNF gene expression in the hippocampus positively correlated with the sucrose preference rate (p < .05).ConclusionFlaxseed oil and flaxseed flour exert antidepressant‐like effect in rats exposed to chronic stress. Flaxseed may have a therapeutic effect on depression.
Highlights
Unpredictable chronic mild stress mimics the environmental stressors that people might experience in daily life
It is widely reported that unexpected chronic stressors could induce various depressionlike behaviors and biochemical abnormalities, such as down-regulation of neurotrophic factors, in animals (Bai et al, 2012, 2014; TA B L E 1 Correlation analysis between the biological indicators and behavioral indicators (r value)
Animal models of depression established by unpredictable chronic mild stress are widely used to evaluate the efficacy of antidepressants (Papp, Panconi, & Gruca, 2004; Zhang et al, 2015)
Summary
Depression is one of the most common mental disorders, and it is characterized by various symptoms, including anhedonia, reduced motivation, and psychomotor retardation. A previous study found that flaxseed secoisolariciresinol diglycoside (SDG, predominant lignan) can prolong the struggling time in despair tests and normalize BDNF expression in ovariectomized mice subjected to unpredictable chronic stress (Ma et al, 2013). These findings suggest potential antidepressant activities of flaxseed associated with BDNF. Studies in animals showed that chronic stress reduced BDNF expression in the hippocampus (Bai et al, 2012), while chronic treatment with antidepressants normalized BDNF levels in the hippocampus and plasma (Molendijk et al, 2011; Russo-Neustadt, Beard, Huang, & Cotman, 2000). The BDNF expression in the hippocampus was measured to further understand the possible mechanism of flaxseed oil and flour
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