Metabolomic Analysis of Fermented Tibetan Tea Using Bacillus circulans and Their Biological Activity on Mice via the Intestine-Hepatic Axis

The use of Bacillus circulans as the sole starter provides better process control compared to natural fermentation. However, the chemical composition of fermented Tibetan tea by B. circulans and its regulatory effects on the intestine-liver axis has not been reported. For this purpose, a high-resolution liquid chromatography tandem mass spectrometry metabolomics approach was performed. The effects of fermented Tibetan tea on the intestine-liver axis of mice were also evaluated. Untargeted metabolomics analysis showed that the contents of catechin derivatives, flavonoids, phenolic acids, and terpenoids increased by 0.3, 2.38, 2.65, and 3.36%, respectively, compared with those before fermentation. Furthermore, 16S ribosomal RNA sequence analysis revealed that the relative abundance of Lactobacillus spp. in the intestine increased after consumption of fermented tea. Additionally, based on histological and quantitative PCR analyses, fermented Tibetan tea also improved intestinal development and intestinal barrier function in mouse, while increasing the antioxidant capacity of mouse liver. Thus, fermented Tibetan tea could provide beneficial health effects through the intestine-liver axis. These findings have facilitated the study of the chemical composition of Tibetan tea and provided theoretical support for its use as a natural beverage with intestinal probiotic functions.

Effects of Pu-erh and Dian Hong tea polyphenols on the gut-liver axis in mice

Tea polyphenols (TP) are the most biologically active components in tea, with antioxidant, antiobesity, and antitumor properties, as well as the ability to modulate the composition and function of intestinal microbiota. This experimental study evaluated the chemical constituents of polyphenols in Pu-erh (PTP) and Dian Hong tea (DHTP). It also investigated the co-regulatory effects of PTP and DHTP on intestinal flora and liver tissues in mice using 16 S rRNA gene and transcriptome sequencing. The results revealed that DHT had higher concentrations of EGC (epigallocatechin), C (catechin), EC (epicatechin), and EGCG (epigallocatechin gallate). In contrast, PT had higher concentrations of GA (gallic acid), ECG (epicatechin-3-gallate), TF (theaflavin), and TB (theabrownin). PTP and DHTP consumption significantly reduced the rates of weight gain in mice. Microbial community diversity was significantly higher in PTP and DHTP-treated mice than in the control group. Notably, beneficial microbes such as Lactobacillus increased significantly in PTP-treated mice, whereas Lachnospiraceae increased significantly in DHTP-treated mice. Both PTP and DHTP improved the activity of the antioxidant enzymes (SOD) and total antioxidant capacity (T-AOC) in the liver. The transcriptome analysis revealed that the beneficial effects of PTP and DHTP were due to changes in various metabolic pathways, the majority of which were related to antioxidant and lipid metabolism. This study discovered that PTP and DHTP had beneficial effects in mice via the gut-liver axis.