Modulation of Lipid-lowering Function and Gut Microbiota in Mice on High-fat Diet by Wuniu Zao Black Tea

To investigate the hypolipidemic function and regulation of gut microbiota of C57BL/6 mice on high-fat diet by aqueous extract of Wuniu Zao black tea. Thirty 8-week-old male C57BL/6 mice were randomly divided into three groups, namely the normal group (NC), the high-fat group (MC) and the Wuniu Zao black tea aqueous extract group (referred to as the black tea group, WBT), to establish a high-fat diet-induced obesity model in mice, and the black tea group was given a gavage dose set at 300 mg/kg tea aqueous extract. Routine indicators such as energy intake, body weight gain, organ index and Lee's index were recorded regularly in mice, and serum biochemical indicators such as glutamic aminotransferase (AST), alanine aminotransferase (ALT), total cholesterol (TC), total triglyceride (TG), low-density lipoprotein (LDL-C), high-density lipoprotein (HDL-C) and glucose tolerance levels were measured, and HE-stained liver histopathological sections were observed. Real-time PCR was applied to detect the mRNA content of six genes such as SREBPlc, PAI-1, FAS, ACC1, SCD1 and CD36 in mouse liver tissues, and Western blot was used to study the expression levels of lipid—regulated proteins. 16S rDNA method was used to analyze the diversity and abundance of gut microbiota and its community structure. The results showed that compared with MC, WBT mice showed significant differences (P<0.05) in body weight (27.5 g), liver index (3.78), serum biochemical indexes (TC:4.31 mmol/L, TG:0.71 mmol/L, LDL-C: 0.47 mmol/L, AST: 74.44 U/L and ALT: 23.93 U/L), and increased but not statistically significant HDL—C levels (2.68 mmol/L); the degree of liver lesions in mice improved. The mRNA expression levels of six genes, including SREBPlc, PAI-1, FAS, ACC1, SCD1 and CD36, were significantly different (P<0.05); protein blotting showed that the expression levels of liver tissue-related proteins, such as SREBPlc, FAS and ACC1, were reduced in WBT mice, accompanied by increased phosphorylation of ACCl(p-ACCl) (P<0.05). The results of 16S rRNA gut micro-biota analysis based on colonic feces showed that the relative abundance of Bacteroidetes (B) and Firmicutes (F) in the intestine of MC mice tended to decrease and increase significantly, respectively, and the ratio of the abundance of both flora {FIB) showed a significant increase; WBT improved the diversity and abundance of gut microbiota in mice by WBT improved the diversity and abundance of gut microbiota, especially the relative abundance of the Firmicutes phylum and the Bacteroidetes phylum, thus improving the disorder of gut microbiota induced by high-fat diet, and thus effectively regulating the normal operation of mouse lipid metabolic pathway. The results showed that the aqueous extract of Wuniu Zao black tea had the effect of regulating lipid metabolism and improving gut microbiota disorders in mice fed a high-fat diet of C57BL/6 mice. © 2024 Chinese Institute of Food Science and Technology. All rights reserved.