Insight into the Interaction of Humulus lupulus L. Specialized Metabolites and Gastrointestinal Bitter Taste Receptors: In Vitro Study in STC-1 Cells and Molecular Docking

Bitter taste receptors, also known as taste 2 receptors (T2R), are expressed throughout the body and are involved in regulating different physiological processes. T2R expression in the intestinal tract regulates orexigenic and anorexigenic peptide secretion, thus becoming potential a potential target for controlling food intake and the prevalence of obesity and overweight. The present study aims to investigate the implication of hop bitter compounds such as α-acids, β-acids, and xanthohumol in the secretion of anorexigenic hormones and T2R expression in intestinal STC-1 cells. The tested bitter compounds induced the secretion of the anorexigenic hormones glucagon-like peptide 1 and cholecystokinin concurrently with a selective increase of murine Tas2r expression. Xanthohumol and α-acids selectively increase Tas2r138 and Tas2r130–Tas2r138 expression, respectively, in STC-1 cells, while β-acids increased the expression of all bitter receptors studied, including Tas2r119, Tas2r105, Tas2r138, Tas2r120, and Tas2r130. Increased intracellular calcium levels confirmed this activity. As all investigated bitter molecules increased Tas2r138 expression, computational studies were performed on Tas2r138 and its human orthologue T2R38 for the first time. Molecular docking experiments showed that all molecules might be able to bind both bitter receptors, providing an excellent basis for applying hop bitter molecules as lead compounds to further design gastrointestinal-permeable T2R agonists.