Chronic mild stressors and diet affect gene expression differently in male and female rats

While depression is reportedly more prevalent in women than men, a neurobiological basis for this difference has not been documented. Chronic mild stress (CMS) is a widely recognized animal model, which uses mild and unpredictable environmental stressors to induce depression. Studies of chronic stress, mainly in males, have reported an increase in the relative intake of "comfort food" as a means of counteracting the effects of stress. This study was designed to test the hypothesis that genes for certain neurotrophic factors, stress markers, and appetite regulators would be expressed differentially in male and female rats exposed to chronic, mild stressors with access to a preferred diet. Gene expression for neuropeptide Y was upregulated in females purely in response to stressors, whereas that for the epidermal growth factor receptor (EGFR) and arginine vasopressin (AVP) in males and fatty acid synthase (FASN) in females responded primarily to diet. Genes for brain-derived neurotrophic factor (BDNF), AVP, and the cocaine-amphetamine regulator of transcription (CART) in males, and leptin in females, showed a significant response to the interaction between stressors and diet. Every affected gene showed a different pattern of expression in males and females. This study confirms the intimate relationship between dietary intake and response to stress at the molecular level, and emphasizes the sex- and gene-specific nature of those interactions. Therefore, it supports a neurobiological basis for differences in the affective state response to stress in males and females.