Gastrointestinal hormone-mediated beneficial bioactivities of bitter polyphenols

Recently, there has been a notable emphasis on the homeostatic regulation by taste receptors expressed in the extra-oral gastrointestinal (GI) tract. Type 2 taste receptors (T2R) are expressed in taste buds that perceive bitter tastes and the GI tract and are activated by ligands. Activation of T2R in the GI tract triggers the release of GI hormones such as cholecystokinin (CCK) or incretin as a glucose-dependent insulinotropic polypeptide (GIP) and glucagon-like peptide-1 (GLP-1). CCK and GLP-1 are peptides that regulate appetite and food intake by influencing GI motility. Incretins also regulate blood glucose homeostasis through insulin secretion. Polyphenols are bioactive compounds commonly found in plant-based food with a strong bitter taste. Additionally, they are not well absorbed by the upper digestive tract and thus tend to move to the colon and get excreted in the feces. Previous epidemiological and intervention studies suggest a negative correlation between polyphenol intake and the risk of diabetes. Beneficial bioactivity associated with polyphenol consumption is proposed to be mediated by the activation of the T2R in GI, consequently improving glucose tolerance and appetite regulation of controlling intestinal motility. This review focused on understanding the interaction between polyphenols and T2Rs and the resulting health benefits on appetite and blood glucose regulation