Betulin Alleviates 5-Fluorouracil-Induced Intestinal Mucositis in Mice

Background: Chemotherapy-induced intestinal mucositis (CIM) is a common gastrointestinal complication of anticancer therapy, and 5-fluorouracil (5-FU) is among the agents most frequently implicated. Betulin (BE), a lupane-type pentacyclic triterpenoid with anti-inflammatory and cytoprotective activities, has not been systematically evaluated in 5-FU-induced CIM. Purpose: This study evaluated the therapeutic effects of BE in a mouse model of 5-FU-induced CIM and examined associated histopathological, apoptotic, inflammatory, and gut microbiota changes. Methods: BALB/c mice received intraperitoneal 5-FU (30 mg/kg/day) for four consecutive days, followed by oral BE at 0, 50, 100, 200, or 400 mg/kg/day for another four days. Clinical manifestations, colon morphometry, blinded descriptive histopathological assessment, apoptosis- and inflammation-related markers, and gut microbiota were assessed. Results: BE treatment alleviated body weight loss, diarrhea, and reduced food intake and was associated with improved colon morphometry and less severe histological injury. At 200 mg/kg, BE treatment was associated with lower Tnf and Nos2 mRNA expression, lower Bax and total caspase-3 protein abundance, higher Bcl-2 protein abundance, and lower iNOS protein abundance. Microbiota analysis of the 200 mg/kg group showed treatment-associated differences in microbial diversity and community composition; these findings were considered exploratory because of the small sample size. Conclusions: BE showed therapeutic potential in 5-FU-induced intestinal mucositis. The molecular and microbiota findings obtained at 200 mg/kg support associations with apoptosis-, inflammation-, and microbiota-related changes but do not establish a definitive mechanism.