Theasinensin A (TSA), a dimer of epigallocatechin gallate, has been preliminarily demonstrated to have hypoglycemia and anti-inflammatory effects. However, little information is available on its potential mechanisms of anti-diabetes. Therefore, the present study aimed to investigate the influence of TSA on glucose and lipid metabolism and gut microbiota in high-fat-diet/streptozotocin-induced diabetic mice. As result, TSA improved polydipsia, polyphagia and impaired glucose tolerance of diabetic mice, declined the fasting blood glucose and hepatic triglyceride level, and enhanced the expression at mRNA level of insulin receptor substrate, phosphoinositide 3-kinase, protein kinase B and glucagon-like peptide 1 receptor (GLP-1R) in the diabetic liver. Moreover, TSA could restore the disorder of gut microbiota of diabetic mice. High-dose (100 mg/kg) TSA showed better beneficial effects from the blood biochemical parameters, hepatic function and gut microbiota. In general, high-dose TSA significantly modulated gut microbiota by increasing the relative abundance of Akkermansia and decreasing the relative abundances of Acetatifactor, Anaerotruncus, Pseudoflavonifactor, Oscillibacter and Clostridium clusters. The results indicated that TSA could exert an anti-diabetes effect in diabetic mice through restoring glucose homeostasis, declining hepatic steatosis, activating insulin and GLP-1 signaling pathways, and ameliorating gut microbiota dysbiosis.

Polysaccharides from Fuzhuan brick tea (FBTPS), one of most important bioactive components in tea, showed various health-promoting functions. Our previous work demonstrated that the crude FBTPS (CFBTPS) could modulate the gut microbiota. However, which purified fraction in CFBTPS contributing to the modulation of gut microbiota remains unclear. Thus, the fermentation characteristics and probiotic activity of a purified fraction (FBTPS-2-1) of CFBTPS were evaluated in this work. The results showed that gut microbiota could utilize FBTPS-2-1 to produce short-chain fatty acids including acetic, propionic, n-butyric and n-valeric acids. FBTPS-2-1 could modulate the structure and metabolic pathways of gut microbiota. FBTPS-2-1 could increase the health-promoting gut microbiota such as Prevotellaceae and Bifidobacteriaceae, and decreased the harmful bacteria such as Enterobacteriaceae and Fusobacteriaceae. The results of metagenomics showed that Prevotella copri and Megamonas funiformis were the dominant bacteria after fermentation of FBTPS-2-1. Furthermore, FBTPS-2-1 could regulate the biosynthesis and metabolism pathways of gut microbiota. Thus, the enrichment of food with FBTPS-2-1 is expected as a potential strategy for promoting human health due to modulation of gut microbiota.