Theabrownin Alleviates Type 2 Diabetes Mellitus in db/db Mice via Modulating LPS/GLP-1 Levels and Restoring Islet Cells: Evidence from Gut–Pancreas Axis

Theabrownin has demonstrated metabolic-modulating effects, but the doses used in previous studies are difficult to achieve through regular tea consumption. This study reassesses its hypoglycemic effects at physiologically relevant doses in the db/db mouse model of type 2 diabetes mellitus (T2DM), with a focus on intestinal microbiota and metabolic pathways. The findings show that theabrownin delays glucose absorption by inhibiting α-glucosidase in the duodenum. It also reduces lipopolysaccharide (LPS)-producing bacteria, increases Akkermansia muciniphila abundance, lowers serum LPS levels, and alleviates β-cell dysfunction due to oxidative stress. Additionally, theabrownin promotes the microbial indole pathway of tryptophan metabolism, enhancing glucagon-like peptide-1 (GLP-1) secretion, which helps mitigate β-cell dysfunction. In conclusion, theabrownin shows potential as a dietary supplement for T2DM treatment, primarily regulating LPS/GLP-1 levels and restoring pancreatic islet function. These findings highlight the potential role of fermented tea in glucose metabolism regulation.