RESUMO
Sesamin and episesamin are the main lignans found in refined sesame oil and have been reported to exert various health benefits. However, the health benefits of these lignans and their molecular mechanisms have not been fully understood. This study evaluated the effects of sesamin, episesamin, and their metabolites on the nuclear bile acid receptor, farnesoid X receptor (FXR, NR1H4), which regulate gene expression involved in bile acid metabolism and gluconeogenesis. By using two different cell-based luciferase reporter assay systems, we found that sesamin, sesamin metabolites, and some episesamin metabolites inhibited FXR activation driven by a bile acid and a synthesized agonist, and it is suggested that these compounds exert their antagonist activity by competing with the FXR agonists on the ligand-binding domain. Sesamin and its major metabolite SC-1 suppressed the expression of several gluconeogenesis-related genes governed by FXR in HepG2 cells but did not affect the expression level of CYP7A1, the rate-limiting enzyme for bile acid synthesis. Dietary sesamin supplementation (AIN-93G supplemented with 0.5% sesamin) led to the decreased hepatic expression of several gluconeogenesis-related genes and reduced blood glucose levels in mice, without adverse effects on bile acid metabolism. These results shed light on the health benefits of taking sesamin and episesamin.