Fermented beet juice reinforces tight junctions and alleviates colitis via multi-pathway regulation

This study investigated the anti-inflammatory and gut-protective effects of fermented beet mixed juice (BM), which contains betanin and levan-like polysaccharides. Chemical characterization of the water-soluble fraction (BM-WS) revealed a complex composition enriched in saccharides and sugar derivatives, including a levan-type structure, as confirmed by GC-MS, ¹H NMR, and GPC analyses. In vitro assays using RAW264.7 and RAW-Blue™ macrophages showed that both BM and BM-WS significantly inhibited LPS-induced nitric oxide (NO) and reactive oxygen species (ROS) production. They also suppressed NF-κB activation and the expression of COX-2 and NLRP3, effects not observed with betanin or commercial levan alone. In a DSS-induced colitis mouse model, BM was given orally together with DSS for 7 days and then continued alone for 3 days. BM markedly reduced the disease activity index, particularly rectal bleeding. BM treatment alleviated histological damage, restored colon length, improved intestinal permeability, and normalized the expression of tight junction proteins. Additionally, BM reduced colonic levels of phosphorylated NF-κB, NLRP3, and apoptotic markers. In DSS-exposed Caco-2 cells, BM attenuated oxidative stress, preserved barrier integrity, suppressed NF-κB and NLRP3 activation, and promoted autophagy. These findings support BM as a multifunctional dietary intervention for ulcerative colitis, offering synergistic antioxidant, anti-inflammatory, and barrier-protective effects that collectively enhance its therapeutic potential beyond the individual components.