Spergularia marina induces glucagon-like peptide-1 secretion in NCI-H716 cells through bile acid receptor activation.

Spergularia marina Griseb. (SM) is a halophyte that grows in mud flats. The aerial portions of SM have been eaten as vegetables and traditionally used to prevent chronic diseases in Korea. However, there has been no scientific report that demonstrates the pharmacological effects of SM. Glucagon-like peptide-1 (GLP-1) is important for the maintenance of glucose and energy homeostasis through acting as a signal in peripheral and neural systems. To discover a functional food for regulating glucose and energy homeostasis, we evaluated the effect of an aqueous ethanolic extract (AEE) of SM on GLP-1 release from enteroendocrine NCI-H716 cells. In addition, we explored the Takeda G-protein-coupled receptor 5 (TGR5) agonist activity of AEE-SM in Chinese hamster ovary (CHO)-K1 cells transiently transfected with human TGR5. As a result, treatment of NCI-H716 cells with AEE-SM increased GLP-1 secretion and intracellular Ca(2+) and cyclic AMP (cAMP) levels in a dose-dependent manner. Transfection of NCI-H716 cells with TGR5-specific small interference RNA inhibited AEE-SM-induced GLP-1 secretion and the increase in Ca(2+) and cAMP levels. Moreover, AEE-SM showed that the TGR5 agonist activity in CHO-K1 cells transiently transfected with TGR5. The results suggest that AEE-SM might be a candidate for a functional food to regulate glucose and energy homeostasis.