The regulatory mechanism of acidic tea polysaccharides from Wuyi rock tea on bile acids in type 2 diabetic rats

ObjectiveThis study aimed to investigate the effects of an acidic tea polysaccharide extracted from Wuyi Rock tea "yellow slice" on bile acids in hyperglycaemic rats.MethodsIn vitro experiments simulating artificial gastric and intestinal fluids were conducted to evaluate the binding capacity of tea polysaccharides to bile salts. The composition of bile acids in the cecal contents was analyzed using Liquid Chromotography with Mass Spectrometry (LC-MS); The relative mRNA expression of bile acid receptors FXR and TGR5 in rat liver and pancreas of rats were measured, along with Western blot analysis of colonic tissues.ResultsThe in vitro experiments demonstrated that tea polysaccharides possess a significant binding capacity for both bound and free bile salts, with stronger affinity for bound bile salts. At 2.00 mg/mL, the binding rate of the tea polysaccharides to sodium cholate were found to be 57.59% and 62.62% for sodium glycylcholate and sodium taurocholate, respectively. In the cecal contents of rats, intervention with tea polysaccharides primarily increased the level of secondary bile acids, including deoxycholic acid and lithocholic acid. Additionlly, the treatment upregulated the mRNA expression of bile acid receptor FXR and TGR5 in the liver and pancreas, with no significant change observed in the expression of GLP-1.ConclusionThe intervention with acidic tea polysaccharides from Wuyi rock tea led to an increased ratio of primary bile acids to secondary bile acids. This suggests that the more hydrophobic secondary bile acids are less effectively absorbed in the enterohepatic circulation.