Objective

Prunella vulgaris L. has long been used for liver protection according to traditional Chinese medicine theory and has been proven by modern pharmacological research to have multiple potential liver-protective effects. However, its effects on non-alcoholic steatohepatitis (NASH) are currently uncertain. Our study explores the effects of P. vulgaris polysaccharides on NASH and intestinal homeostasis.

Methods

An aqueous extract of the dried fruit spikes of P. vulgaris was precipitated in an 85% ethanol solution (PVE85) to extract crude polysaccharides from the herb. A choline-deficient, L-amino acid-defined, high-fat diet (CDAHFD) was administrated to male C57BL/6 mice to establish a NASH animal model. After 4 weeks, the PVE85 group was orally administered PVE85 (200 mg/[kg·d]), while the control group and CDAHFD group were orally administered vehicle for 6 weeks. Quantitative real-time polymerase chain reaction analysis, Western blotting, immunohistochemistry and other methods were used to assess the impact of PVE85 on the liver in mice with NASH. 16S rRNA gene amplicon analysis was employed to evaluate the gut microbiota abundance and diversity in each group to examine alterations at various taxonomic levels.

Results

PVE85 significantly reversed the course of NASH in mice. mRNA levels of inflammatory mediators associated with NASH and protein expression of hepatic nucleotide-binding leucine-rich repeat and pyrin domain-containing protein 3 (NLRP3) were significantly reduced after PVE85 treatment. Moreover, PVE85 attenuated the thickening and cross-linking of collagen fibres and inhibited the expression of fibrosis-related mRNAs in the livers of NASH mice. Intriguingly, PVE85 restored changes in the gut microbiota and improved intestinal barrier dysfunction induced by NASH by increasing the abundance of Actinobacteria and reducing the abundance of Proteobacteria at the phylum level. PVE85 had significant activity in reducing the relative abundance of Clostridiaceae at the family levels. PVE85 markedly enhanced the abundance of some beneficial micro-organisms at various taxonomic levels as well. Additionally, the physicochemical environment of the intestine was effectively improved, involving an increase in the density of intestinal villi, normalization of the intestinal pH, and improvement of intestinal permeability.

Conclusion

PVE85 can reduce hepatic lipid overaccumulation, inflammation, and fibrosis in an animal model of CDAHFD-induced NASH and improve the intestinal microbial composition and intestinal structure.

Key words: Prunella vulgaris L., Crude polysaccharides, Non-alcoholic steatohepatitis, Gut microbiota