Combined effects of calorie restriction and chronic stress on systemic inflammation and gut microbiota in rats exposed to Leptospira interrogans lipopolysaccharide

BACKGROUND: Calorie restriction (CR) is widely studied for its anti-inflammatory and immunomodulatory effects. However, under conditions of chronic stress-such as those experienced during war, displacement, or famine-its impact on immune function remains poorly understood. In such contexts, combined nutritional and psychosocial stress may exacerbate inflammation and compromise host defences against pathogens. OBJECTIVE: To investigate how the combination of moderate calorie restriction and chronic social stress affects systemic immune responses and gut microbiota composition following exposure to Leptospira interrogans lipopolysaccharide (LPS) in rats. METHODS: Male Wistar rats were assigned to either ad libitum feeding (control) (n = 6), calorie restriction (CR, 30 % reduction) (n = 12), or CR combined with chronic overcrowding stress for 14 days (n = 12). All animals were subsequently challenged with Leptospira LPS. Immune gene expression was analyzed in peripheral blood using RT-qPCR arrays. Culture-based quantification of fecal microbiota was performed to assess compositional changes. Correlations between microbiota and cytokine gene expression were evaluated. RESULTS: Compared with the control group, CR increased Il10 expression and increased the abundance of beneficial bacteria such as Lactobacillus and Bifidobacterium, suggesting an anti-inflammatory and microbiota-supportive effect. In contrast, relative to the CR-only group, rats exposed to CR combined with chronic social stress showed marked upregulation of pro-inflammatory cytokine genes (Il1b, Il6, Tnf) and a shift toward gut dysbiosis, characterized by increased abundance of Klebsiella spp., Escherichia coli, and Enterococcus species. CONCLUSION: A combination of chronic stress and calorie restriction can promote inflammation and cause gut dysbiosis, which may lead to a more severe form of leptospirosis.