Bitter gourd (Momordica Charantia L.) stimulates the secretion of the incretin Glucagon-like peptide-1 by enteroendocrine cells in vitro

The Glucagon-like peptide-1 hormone (GLP-1) is a key insulinotropic and glucagonostatic incretin produced by the L enteroendocrine cells (EECs) of the intestines. On the luminal side, EECs express a variety of taste receptors, among them, members of the bitter taste receptor family or taste receptors type 2 (TAS2Rs).

The fruit of the Momordica charantia is called bitter gourd (BG) and has a distinctive bitter taste. This edible vegetable, common in tropical regions, is also a folk medicine employed for the management of type-2 Diabetes.

Within the last decade, there has been increasing evidence on chemosensory activity of EECs, and how food tastants can affect the secretion of intestinal hormones, presumably, by interacting with sweet, umami, and/or bitter taste receptors. We hypothesized that the hypoglycaemic properties of BG (or a part of it) would be based on the stimulation of GLP-1 secretion by EECs, likely through interaction with TAS2Rs.

Here, we studied the GLP-1 secretion by in vitro EECs (mouse and human) when exposed to different BG specimens (genotypes and extracts). BG samples significantly induced GLP-1 secretion in mouse STC-1 and in human HuTu-80 EECs. Besides, TAS2R16 responded dose-dependently to BG extracts, suggesting its potential involvement in the interaction between BG and EECs. Based on the two EEC in vitro models, the GLP-1 secretion induced by different BG cultivars was correlated with antidiabetic effects as found in an in vivo piglet study. The role of GLP-1 secretion in BG’s antidiabetic effects and the difference between both cell-based models will be discussed.