Impact of stool transplantation and metformin on polyp reduction and inflammation in an APC Min mouse model

Familial adenomatous polyposis is a hereditary condition characterized by numerous adenomatous polyps in the colon and rectum, significantly increasing colorectal cancer risk. Current management strategies, such as prophylactic colectomy, are invasive and have long-term consequences, highlighting the need for alternative therapies. This study aimed to evaluate whether stool transplantation and metformin therapy synergistically reduce polyp formation and inflammation.

APC Min mice were divided into 4 groups: control, anti-control (antibiotic pretreatment), stool (stool transplantation), and stool+metformin. Polyp burden, bacterial abundance, inflammatory cytokines (interleukin [IL]-6, tumor necrosis factor [TNF]-α, IL-10), and tumorigenic markers (NF-κB, Cox2, c-myc, β-catenin) were assessed using messenger RNA (mRNA) and protein analyses of intestinal tissues, along with serum and fecal microbiota evaluations.

Stool transplantation combined with metformin significantly reduced bacterial abundance and polyp burden. The anti-control group showed similar reductions, suggesting suppression of gut microbiota re-establishment. TNF-α and IL-10 levels remained unchanged, but a significant increase in IL-6 was observed in the stool+metformin group's intestinal tissues, indicating localized immune activation. Intestinal Cox2 mRNA expression was reduced in the combination group, correlating with polyp suppression. Protein levels of NF-κB, Cox2, and β-catenin showed no significant changes in vivo, while in vitro experiments revealed a decrease in NF-κB and an increase in Cox2, suggesting complex regulation of inflammation-related pathways.

Stool transplantation combined with metformin reduces polyp burden in APC Min mice through gut microbiota modulation and localized immune activation. These findings support the therapeutic potential of this combination treatment for familial adenomatous polyposis.