P0023 Methionine Restriction Promotes Intestinal Mucosal Repair by Regulating Selenbp1 and Modulating Macrophage Polarization

Abstract Background Intestinal epithelial homeostasis is critical for maintaining gut integrity and function. Methionine is an essential amino acid involved in various cellular processes, and its dietary regulation may impact intestinal injury and repair mechanisms. Selenbp1, an oxidase of the methionine metabolite methanethiol, plays an important role in this process. This study investigates the role of methionine intake and Selenbp1 in colonic injury and epithelial repair. Methods Animal models with radiation-induced intestinal injury were used to assess the effects of methionine restriction and supplementation. Intestinal epithelial-specific knockout of Selenbp1 and control mice were used for in vivo experiments. Colonic organoids, macrophage co-culture assays, and biochemical assays, including qPCR, immunoblotting, and flow cytometry, were employed to study epithelial proliferation, SUMOylation of Satb2, and macrophage polarization. Clinical samples from patients with Crohn's disease were also analyzed for macrophage markers, as well as Satb2 and SUMO2/3 expression levels. Results Methionine restriction alleviated radiation-induced colonic injury in mice, as evidenced by improved histological scores and reduced inflammatory markers. In contrast, high methionine levels decreased Selenbp1 expression in the colon. Intestinal epithelial-specific Selenbp1 knockout exacerbated radiation-induced colonic mucosal injury, with significantly lower organoid survival rates and budding efficiency post-irradiation. However, this detrimental effect of Selenbp1 knockout was reversed upon methionine restriction, demonstrating the potential of dietary modulation. Furthermore, methionine supplementation led to a reduction in the SUMOylation of Satb2, a key regulator of intestinal epithelial homeostasis. The lower the level of Satb2 SUMOylation, the higher the clinical pathological features of Crohn's disease, such as disease activity. In co-culture assays, methionine supplementation enhanced M1 polarization of macrophages, further indicating a role of methionine in modulating immune responses. In clinical Crohn's disease (CD) specimens, we also found that a higher proportion of M1 macrophages correlated with lower expression levels of Selenbp1. Conclusion Methionine restriction promotes intestinal mucosal repair by regulating Selenbp1 and macrophage polarization, suggesting its potential as a therapeutic strategy for colonic repair.