Abstract
Taste stimulants play important roles in triggering digestion and absorption of nutrients and in toxin detection, under the control of the gut-brain axis. Bitter compounds regulate gut hormone secretion and gastrointestinal motility through bitter taste receptors (TAS2Rs) located in the taste buds on the tongue and in the enteroendocrine cells. Gastric accommodation (GA) is an important physiologic function. However, the role of TAS2R agonists in regulating GA remains unclear. To clarify whether GA is influenced by bitter stimulants, we examined the effect of TAS2R agonist denatonium benzoate (DB), administered intraorally and intragastrically, by measuring the consequent intrabag pressure in the proximal stomach of guinea pigs. Effects of the Kampo medicine rikkunshito (RKT) and its bitter components liquiritigenin and naringenin on GA were also examined. Intraoral DB (0.2 nmol/ml) administration enhanced GA. Intragastric DB administration (0.1 and 1 nmol/kg) promoted GA, whereas higher DB doses (30 μmol/kg) inhibited it. Similar changes in GA were observed with intragastric (1000 mg/kg) and intraoral (200 mg/ml) RKT administration. Liquiritigenin and naringenin also promoted GA. These findings suggest that GA is affected by the stimulation of TAS2Rs in the oral cavity or gut in guinea pigs.
Highlights
Human beings can distinguish between five basic taste qualities—sweet, sour, bitter, salty, and umami (Barretto et al, 2015)
To clarify whether Gastric accommodation (GA) is influenced by bitter stimulants, we examined the effect of bitter taste receptor (TAS2R) agonist denatonium benzoate (DB), administered intraorally and intragastrically, by measuring the consequent intrabag pressure in the proximal stomach of guinea pigs
The GA-promoting effect of DB could be mediated by a gut hormone or a direct action on smooth muscle cells in guinea pigs
Summary
Human beings can distinguish between five basic taste qualities—sweet, sour, bitter, salty, and umami (Barretto et al, 2015). Sensing the luminal content through taste receptors is important to initiation of appropriate responses to digestion and absorption of nutrients, which are regulated via the gut-brain axis (Daly et al, 2012; Janssen and Depoortere, 2013). Twenty-five TAS2R subtypes have been identified in humans and are considered as playing a role in the detection of toxins. These receptors affect the secretion of gut hormone and regulate GI motility (Wu et al, 2002; Shi et al, 2003; Chen et al, 2006; Rozengurt and Sternini, 2007; Hao et al, 2008; Jeon et al, 2008; Janssen et al, 2011; Daly et al, 2013)
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