Polygonum tinctorium leaf extract ameliorates high-fat diet-induced intestinal epithelial damage in mice.

Dietary fat strongly influences the intestinal mucosal barrier, which protects against invading pathogenic bacteria. A high-fat diet (HFD) compromises the integrity of epithelial tight junctions (TJs) and reduces mucin production, leading to intestinal barrier disruption and metabolic endotoxemia. It has been shown that the active constituents of indigo plants can protect against intestinal inflammation; however, their protective role in HFD-induced intestinal epithelial damage remains unknown. The present study aimed to investigate the effects of Polygonum tinctorium leaf extract (indigo Ex) on HFD-induced intestinal damage in mice. Male C57BL6/J mice were fed a HFD and injected intraperitoneally with either indigo Ex or phosphate-buffered saline (PBS) for 4 weeks. The expression levels of TJ proteins, zonula occludens-1 and Claudin-1, were analyzed by immunofluorescence staining and western blotting. The colon mRNA expression levels of tumor necrosis factor-α, interleukin (IL)-12p40, IL-10 and IL-22 were measured by reverse transcription-quantitative PCR. The results revealed that indigo Ex administration attenuated the HFD-induced shortening of the colon. Colon crypt length was shown to be significantly greater in the indigo Ex-treated group mice compared with that in the PBS-treated group mice. Moreover, indigo Ex administration increased the number of goblet cells, and ameliorated the redistribution of TJ proteins. Notably, indigo Ex significantly increased the colon mRNA expression levels of IL-10. Indigo Ex displayed little effect on the gut microbial composition of HFD-fed mice. Taken together, these results suggested that indigo Ex may protect against HFD-induced epithelial damage. The leaves of indigo plants contain promising natural therapeutic compounds that could be used to treat obesity-associated intestinal damage and metabolic inflammation.