Figure 4

High gut succinate levels induce C. difficile proliferation and cause gut inflammation. (A) Assessment of C. difficile in vitro study at 48 h. 1: control group without C. difficile inoculation (Control (−)), 2: control group with C. difficile inoculation (Control (+)), 2–8: treatment group with succinate 0–0.5 mg/ml under fidaxomicin 0.01 μg/ml. The testing detectable level is above 2.0 (log amount) per ml of medium, data shown as mean ± SD (n = 5 per group). (B) Concentration of organic acids in the medium. Samples were taken at 24 h (left) and 48 h (right). All values are mean ± SD (n = 5). (C) Tumor necrosis factor-α (TNF-α) protein concentration in mice colon tissue detected at day 5. All values are mean ± SD (n = 5–10). (D) Representative flow cytometry plots of identified macrophages (F40/80⁺/CD11b⁺), and tumor necrosis factor-α (TNF-α) producing macrophage (F40/80⁺/CD11b⁺/TNF-α⁺) expression among lymphocytes in the colonic lamina propria (cLP) in the control group (Control), and the other group with succinate administration for 4 days (Add succinate). Percentage of TNF-α secreting macrophages in macrophages (right).