The differential alleviation of DSS-induced colitis in mice by black tea extracts of different origins <i>via</i> enhancing the gut barrier and gut microbiota modulation

Black tea is commonly used for tea beverage production and has been shown to be an effective natural ingredient to prevent experimentally induced colitis. However, there is limited evidence to show whether black teas of different origins demonstrate similar anti-inflammatory capacity in mice with colitis. In this study, mice were administered daily black tea extracts of lapsang, keemun or dianhong for 1 week prior to receiving 4% dextran sulfate sodium for inducing colitis. Both the lapsang and keemun extracts exhibited better anti-inflammatory effects than dianhong extract, as evidenced by the former two tea extracts enhancing intestinal barrier functions (up-regulation of MUC2 and ZO-1 and increased population of goblet cells) and decreasing colonic and serum pro-inflammatory cytokines. We deduced that gallocatechin (GC) might be a key contributor to the anti-colitis effects of black tea, potentially through synergistic interactions with other components at an optimal ratio to enhance the anti-inflammatory efficacy. Fecal microbiome analysis showed that the gut microbiome was differentially modulated by the lapsang and keemun extracts. Their anti-colitic effects were dependent on the gut microbiome, as shown by the loss of such protection in DSS mice treated with broad-spectrum antibiotics (ABX) for significant microbiome alterations. Mechanistically, colonic transcriptomic analysis showed the differential impacts of lapsang and keemun extracts on colitis <i>via</i> modulating the gene expressions of the glutamatergic synapse and IL-17 pathway, respectively. Further qPCR and immunohistochemistry assays verified the aforementioned pathway modulation. Together, our study provides a roadmap for understanding the effects of different black tea types on colitis and for providing potential directions for the nutritional modulation of colitis.