Mechanism of Phyllanthus emblica polyphenols in alleviating DSS-induced ulcerative colitis: Insights from transcriptomics and microbiome analysis

The fruit of Phyllanthus emblica (PE) is a 'drug homologous food' that is rich in polyphenols for treating inflammatory diseases. Nevertheless, the ability of PE polyphenols (PEP) to alleviate ulcerative colitis (UC) remains unclear. The aim of this study was to reveal the chemical composition of PEP and its therapeutic potential for treating UC. In this study, PEP was purified with an NKA-2 macroporous resin and identified via liquid chromatography combined with mass spectrometry (LC‒MS). Furthermore, a dextran sulfate sodium salt-induced UC mice model was used to evaluate the ability of PEP to alleviate UC. The symptoms, histopathology, expression of inflammatory cytokines, mucus and tight junction levels, changes in the gut microbiome and colon transcriptomics of UC mice were assessed after PEP intervention. The results suggested that PEP strikingly improved weight loss, disease activity index scores, colon length changes and histopathological damage. Moreover, PEP inhibited the expression of serum proinflammatory cytokines (TNF-α, IL-1β, and IL-6) and sustained intestinal integrity by increasing the expression of Mucin 2, Zonula occludens 1 and Occludin. 16S rRNA sequencing revealed that PEP regulated disorders of the gut microflora related to inflammation and the mucus barrier, including Escherichia_Shigella, Rikenellaceae_RC9_gut_group, Bacteroides, Muribaculaceae, Helicobacter and Anaerostipes. Transcriptome sequencing analysis, western blotting, and immunohistochemistry confirmed that PEP regulated reversed genes as well as effector proteins enriched in the PPAR signaling pathway (PPARγ, MMP1, CYP4A12A, and UCP1) and the Wnt/β-catenin signaling pathway (Wnt8B, FZD9, GSK3β, p-GSK3β, β-catenin, Axin2 and Lgr5). These findings indicate that PEP has therapeutic potential for alleviating UC and could serve as a functional dietary supplement.